GS 9883, bictegravir

CAS 1611493-60-7

PHASE 3

HIV-1 integrase inhibitor

(2R,5S,13aR)-8-hydroxy-7,9-dioxo-N-[(2,4,6-trifluorophenyl)methyl]-2,3,4,5,7,9,13,13a-octahydro-2,5-methanopyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazepine-10-carboxamide

2,5-Methanopyrido(1′,2′:4,5)pyrazino(2,1-b)(1,3)oxazepine-10-carboxamide, 2,3,4,5,7,9,13,13a-octahydro-8-hydroxy-7,9-dioxo-N-((2,4,6-trifluorophenyl)methyl)-, (2R,5S,13aR)-

2,5-Methanopyrido(1′,2′:4,5)pyrazino(2,1-b)(1,3)oxazepine-10-carboxamide, 2,3,4,5,7,9,13,13a-octahydro-8-hydroxy-7,9-dioxo-N-((2,4,6-trifluorophenyl)methyl)-, (2R,5S,13aR)-

(2R,5S,13aR)-8-hydroxy-7,9-dioxo-N-(2,4,6-trifluorobenzyl)-2,3,4,5,7,9,13,13a-octahydro-2,5-methanopyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazepine-10-carboxamide

(2 ,5S,13aI )-8-hydroxy-7,9-dioxo-N-(2,4,6-trifluoroheoctahydro-2,5-methanopyrido[ 1 ‘,2’:4,5]pyrazino[2, 1 -b][ 1 ,3]oxazepine- 10-carboxamide

MF  C₂₁H₁₈F₃N₃O_5,

 UNII-8GB79LOJ07; 8GB79LOJ07

BICTEGRAVIR

• 16 Nov 2015 Phase-III clinical trials in HIV-1 infections (Combination therapy, Treatment-naive) in USA (PO) (Gilead Pipeline, November 2015)
• 01 Jul 2015 Gilead Sciences completes a phase I trial in HIV-1 infections in USA and New Zealand (NCT02400307)
• 01 Apr 2015 Phase-I clinical trials in HIV-1 infections (In volunteers) in New Zealand (PO) (NCT02400307)

UPDATE       Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide); Gilead; For the treatment of HIV-1 infection in adults, Approved February 2018

Human immunodeficiency virus infection and related diseases are a major public health problem worldwide. Human immunodeficiency virus type 1 (HIV-1) encodes three enzymes which are required for viral replication: reverse transcriptase, protease, and integrase. Although drugs targeting reverse transcriptase and protease are in wide use and have shown effectiveness, particularly when employed in combination, toxicity and development of resistant strains have limited their usefulness (Palella, et al. N. Engl. J Med. (1998) 338:853-860; Richman, D. D. Nature (2001) 410:995-1001). Accordingly, there is a need for new agents that inhibit the replication of HIV and that minimize PXR activation when co-administered with other drugs.

Certain polycyclic carbamoylpyridone compounds have been found to have antiviral activity, as disclosed in PCT/US2013/076367. Accordingly, there is a need for synthetic routes for such compounds.

SYNTHESIS

WO 2014100323

PATENTS

WO2014100323

xample 42

Preparation of Compound 42

(2 ,5S,13aI )-8-hydroxy-7,9-dioxo-N-(2,4,6-trifluorohe

octahydro-2,5-methanopyrido[ 1 ‘,2’:4,5]pyrazino[2, 1 -b][ 1 ,3]oxazepine- 10-carboxamide

42

Step 1

l-(2,2-dimethoxyethyl)-5-methoxy-6-(methoxycarbonyl)-4-oxo-l ,4-dihydropyridine-3-carboxylic acid (3.15 g, 10 mmol) in acetonitrile (36 mL) and acetic acid (4 mL) was treated with methanesuffhnic acid (0.195 mL, 3 mmol) and placed in a 75 deg C bath. The reaction mixture was stirred for 7 h, cooled and stored at -10 °C for 3 days and reheated to 75 °C for an additional 2 h. This material was cooled and carried on crude to the next step.

Step 2

Crude reaction mixture from step 1 (20 mL, 4.9 mmol) was transferred to a flask containing (lR,3S)-3-aminocyclopentanol (0.809 g, 8 mmol). The mixture was diluted with acetonitrile (16.8 mL), treated with potassium carbonate (0.553 g, 4 mmol) and heated to 85 °C. After 2 h, the reaction mixture was cooled to ambient temperature and stirred overnight. 0.2M HQ (50 mL) was added, and the clear yellow solution was extracted with dichloromethane (2×150 mL). The combined organic layers were dried over sodium sulfate, filtered and concentrated to 1.49 g of a light orange solid. Recrystallization from dichloimethane:hexanes afforded the desired intermediate 42 A: LC S-ESI (m/z): [M+H]+ calculated for Ci5Hi7N206: 321.1 1 ; found: 321.3.

Step 3

Intermediate 42-A (0.225 g, 0.702 mmol) and (2,4,6-trifluorophenyl)methanamine (0.125 g, 0.773 mmol) were suspended in acetonitrile (4 mL) and treated with N,N-diisopropylethylamine (DIPEA) (0.183 mmol, 1.05 mmol). To this suspension was added (dimethyiammo)- V,A/-dimethyi(3H-[l ,2,3]triazolo[4,5-&]pyridm~3-yiox.y)methammimum hexafluorophosphate (HATU, 0.294 g, 0.774 mmol). After 1.5 hours, the crude reaction mixture was taken on to the next step. LfJMS-ESlT (m/z): [M+H calculated for (\ ,l l.,, i \\:0< : 464.14; found: 464.2.

Step 4

To the crude reaction mixture of the previous step was added MgBr2

(0.258 g, 1.40 mmol). The reaction mixture was stirred at 50 °C for 10 minutes, acidified with 10% aqueous HC1, and extract twice with dichloromethane. The combined organic phases were dried over MgS04, filtered, concentrated, and purified by silica gel chromatography (EtOH/dichlormethane) followed by HPLC (ACN H2O with 0.1 % TFA modifier) to afford compound 42: 1H~ M (400 MHz, DMSO-</6) δ 12.43 (s, 1H), 10.34 (t, J = 5.7 Hz, IH), 8.42 (s, 1H), 7.19 (t, J = 8.7 Hz, 2H), 5.43 (dd, ./’ 9.5, 4.1 Hz, I H), 5.08 (s, i l l ). 4.66 (dd, ./ 12.9, 4.0 Hz, IH), 4.59 (s, 1 1 1 ). 4.56 4.45 (m, 2H), 4.01 (dd, J = 12.7, 9.7 Hz, IH), 1.93 (s, 4H), 1.83 (d, J —— 12.0 Hz, I H),

1.56 (dt, J = 12.0, 3.4 Hz, I H). LCMS-ESI+ (m/z): [M+H]+ calculated for { · Ί ί ] ΝΓ :Χ.¾ϋ : 450.13; found: 450.2.

PATENT

WO2015177537

https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2015177537&recNum=1&maxRec=&office=&prevFilter=&sortOption=&queryString=&tab=PCTDescription

PATENT

WO2015196116

https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2015196116&redirectedID=true

PATENT

WO2015196137

https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2015196137&recNum=1&maxRec=&office=&prevFilter=&sortOption=&queryString=&tab=PCTDescription

PATENT

http://www.google.com/patents/US20140221356

Example 42 Preparation of Compound 42 (2R,5S,13aR)-8-hydroxy-7,9-dioxo-N-(2,4,6-trifluorobenzyl)-2,3,4,5,7,9,13,13a-octahydro-2,5-methanopyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazepine-10-carboxamide

Step 1

• 1-(2,2-dimethoxyethyl)-5-methoxy-6-(methoxycarbonyl)-4-oxo-1,4-dihydropyridine-3-carboxylic acid (3.15 g, 10 mmol) in acetonitrile (36 mL) and acetic acid (4 mL) was treated with methanesulfonic acid (0.195 mL, 3 mmol) and placed in a 75 deg C. bath. The reaction mixture was stirred for 7 h, cooled and stored at −10° C. for 3 days and reheated to 75° C. for an additional 2 h. This material was cooled and carried on crude to the next step.

Step 2

• Crude reaction mixture from step 1 (20 mL, 4.9 mmol) was transferred to a flask containing (1R,3S)-3-aminocyclopentanol (0.809 g, 8 mmol). The mixture was diluted with acetonitrile (16.8 mL), treated with potassium carbonate (0.553 g, 4 mmol) and heated to 85° C. After 2 h, the reaction mixture was cooled to ambient temperature and stirred overnight. 0.2M HCl (50 mL) was added, and the clear yellow solution was extracted with dichloromethane (2×150 mL). The combined organic layers were dried over sodium sulfate, filtered and concentrated to 1.49 g of a light orange solid. Recrystallization from dichlormethane:hexanes afforded the desired intermediate 42A: LCMS-ESI⁺ (m/z): [M+H]⁺ calculated for C15H₁₇N₂O₆: 321.11; found: 321.3.

Step 3

• Intermediate 42-A (0.225 g, 0.702 mmol) and (2,4,6-trifluorophenyl)methanamine (0.125 g, 0.773 mmol) were suspended in acetonitrile (4 mL) and treated with N,N-diisopropylethylamine (DIPEA) (0.183 mmol, 1.05 mmol). To this suspension was added (dimethylamino)-N,N-dimethyl(3H-[1,2,3]triazolo[4,5-b]pyridin-3-yloxy)methaniminium hexafluorophosphate (HATU, 0.294 g, 0.774 mmol). After 1.5 hours, the crude reaction mixture was taken on to the next step. LCMS-ESI⁺ (m/z): [M+H]⁺ calculated for C₂₂H₂₁F₃N₃O₅: 464.14; found: 464.2.

Step 4

• To the crude reaction mixture of the previous step was added MgBr₂ (0.258 g, 1.40 mmol). The reaction mixture was stirred at 50° C. for 10 minutes, acidified with 10% aqueous HCl, and extract twice with dichloromethane. The combined organic phases were dried over MgSO₄, filtered, concentrated, and purified by silica gel chromatography (EtOH/dichlormethane) followed by HPLC (ACN/H₂O with 0.1% TFA modifier) to afford compound 42: ¹H-NMR (400 MHz, DMSO-d₆) δ 12.43 (s, 1H), 10.34 (t, J=5.7 Hz, 1H), 8.42 (s, 1H), 7.19 (t, J=8.7 Hz, 2H), 5.43 (dd, J=9.5, 4.1 Hz, 1H), 5.08 (s, 1H), 4.66 (dd, J=12.9, 4.0 Hz, 1H), 4.59 (s, 1H), 4.56-4.45 (m, 2H), 4.01 (dd, J=12.7, 9.7 Hz, 1H), 1.93 (s, 4H), 1.83 (d, J=12.0 Hz, 1H), 1.56 (dt, J=12.0, 3.4 Hz, 1H). LCMS-ESI⁺ (m/z): [M+H]⁺ calculated for C₂₁H₁₉F₃N₃O₅: 450.13; found: 450.2.

PATENT

WO-2015195656

General Scheme I:

General Scheme II:

General Scheme II

General Scheme III:

General Scheme III

General Scheme IV:

G-1

General Scheme V:

II

EXAMPLES

In order for this invention to be more fully understood, the following examples are set forth. These examples are for the purpose of illustrating embodiments, and are not to be construed as limiting the scope of this disclosure in any way. The reactants used in the examples below may be obtained either as described herein, or if not described herein, are themselves either commercially available or may be prepared from commercially available materials by methods known in the art.

In one embodiment, a multi-step synthetic method for preparing a compound of Formula I is provided, as set forth below. In certain embodiments, each of the individual steps of the Schemes set forth below is provided. Examples and any combination of two or more successive steps of the below Examples are provided.

A. Acylation and amidation of Meldrum ‘s acid to form C-la:

[0520] In a reaction vessel, Meldrum’s acid (101 g, 1.0 equivalent) and 4-dimethylaminopyridine (1.8 g, 0.2 equivalents) were combined with acetonitrile (300 mL). The resulting solution was treated with methoxyacetic acid (6.2 mL, 1.2 equivalents). Triethylamine (19.4 mL, 2.0 equivalents) was added slowly to the resulting solution, followed by pivaloyl chloride (9.4 mL, 1.1 equivalents). The reaction was then heated to about 45 to about 50 °C and aged until consumption of Meldrum’s acid was deemed complete.

A separate reaction vessel was charged with acetonitrile (50 mL) and J-la (13.4 g, 1.2 equivalents). The resulting solution was treated with trifluoroacetic acid (8.0 mL, 1.5 equivalents), and then this acidic solution was added to the acylation reaction in progress at about 45 to about 50 °C.

The reaction was allowed to age for at least 18 hours at about 45 to about 50 °C, after which time the solvent was removed under reduced pressure. The crude residue was dissolved in ethyl acetate (150 mL), and the organic layer was washed with water. The combined aqueous layers were extracted with ethyl acetate. The combined organic layers were washed with saturated sodium bicarbonate solution, and the combined bicarbonate washes were back extracted with ethyl acetate. The combined organic layers were dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The resulting crude material was purified twice via silica gel chromatography to yield C-la.

^lH NMR (400 MHz, CDC1₃): δ 7.12 (br, 1H), 6.66 (app t, J= 8.1 Hz, 2H), 4.50 (app d, J= 5.7 Hz, 2H), 4.08 (s, 2H), 3.44 (s, 2H), 3.40 (s, 3H). ¹³C NMR (100 MHz, CDC1₃): δ 203.96, 164.90, 162.37 (ddd, J= 250.0, 15.7, 15.7 Hz), 161.71 (ddd, J = 250.3, 14.9, 10.9 Hz), 110.05 (ddd, J= 19.7, 19.7, 4.7 Hz), 100.42 (m), 77.58, 59.41, 45.71, 31.17 (t, J= 3.5 Hz). LCMS, Calculated: 275.23, Found: 275.97 (M).

I l l

B. Alkylation of C-la to form E-la:

A solution of C-la (248 mg, 1.0 equivalent) and 2-methyl tetrahydrofuran (1.3 niL) was treated with N,N-dimethylformamide dimethylacetal (0.1 mL, 1.1 equivalent) and stirred at room temperature overnight (~14 hours). The reaction was treated with aminoacetaldehyde dimethyl acetal (0.1 mL, 1.0 equivalents), and was allowed to age for about 2 hours, and then was quenched via the addition of 2 Ν HC1

(1.5 mL).

The reaction was diluted via the addition of ethyl acetate, and phases were separated. The aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The crude residue was purified via silica gel chromatography to yield E-la.

¹H NMR (400 MHz, CDC1₃): δ 10.85 (s, 1H), 9.86 (s, 1H), 8.02 (d, J= 13.1 Hz, 1H), 6.65 (dd, J= 8.7, 7.7 Hz, 2H), 4.53 (d, J= 3.9 Hz, 2H), 4.40 (t, J= 5.1 Hz, 1H), 4.18 (s, 2H), 3.42 (s, 6H), 3.39 (m, 2H), 3.37 (s, 3H). ¹³C MR (100 MHz, CDC1₃): δ 193.30, 169.15, 162.10 (ddd, J= 248.9, 15.5, 15.5 Hz), 161.7 (ddd, J =

250.0, 14.9, 1 1.1 Hz), 161.66, 1 11.08 (ddd J= 19.9, 19.9, 4.7 Hz) 103.12, 100.29 (ddd, J= 28.1, 17.7, 2.3 Hz), 76.30, 58.83, 54.98, 53.53, 51.57, 29.89 (t, J= 3.3 Hz). LCMS, Calculated: 390.36, Found: 390.92 (M).

c. Cyclization of E-la to form F-la:

E-1a F-1a

] E-la (0.2 g, 1.0 equivalent), dimethyl oxalate (0.1 g, 2.5 equivalents) and methanol (1.5 mL) were combined and cooled to about 0 to about 5 °C. Sodium methoxide (0.2 mL, 30% solution in methanol, 1.75 equivalents) was introduced to the reaction slowly while keeping the internal temperature of the reaction below about 10 °C throughout the addition. After the addition was completed the reaction was heated to about 40 to about 50 °C for at least 18 hours.

After this time had elapsed, the reaction was diluted with 2 N HC1 (1.5 mL) and ethyl acetate (2 mL). The phases were separated, and the aqueous phase was extracted with ethyl acetate. The combined organic layers were washed with brine, dried over magnesium sulfate, filtered, and solvent was removed under reduced pressure. The resulting crude oil was purified via silica gel chromatography to afford F-la.

^lR NMR (400 MHz, CDC1₃): δ 10.28 (t, J= 5.5 Hz, 1H), 8.38 (s, 1H), 6.66 – 6.53 (m, 2H), 4.58 (d, J= 5.6 Hz, 2H), 4.43 (t, J= 4.7 Hz, 1H), 4.00 (d, J= 4.7 Hz, 2H), 3.92 (s, 3H), 3.88 (s, 3H), 3.32 (s, 6H). ¹³C NMR (100 MHz, CDC1₃): δ 173.08, 163.81, 162.17, 162.14 (ddd, J= 249.2, 15.6, 15.6 Hz), 161.72 (ddd, J= 250.5, 15.0, 10.9 Hz), 149.37, 144.64, 134.98, 119.21, 1 10.53 (ddd, J= 19.8, 4.7, 4.7 Hz), 102.70, 100.22 (m), 60.68, 56.75, 55.61, 53.35, 30.64. LCMS, Calculated: 458.39, Found: 459.15 (M+H).

D. Alkylation and cyclization of C-la to form F-la:

1 . DMFDMA

C-1a NaOMe, MeOH, 40 °C F-1a

To a reaction vessel were added C-la (245 mg, 1.0 equivalent) and N,N-dimethylformamide dimethylacetal (0.5 mL, 4.3 equivalent). The reaction mixture was agitated for approximately 30 minutes. The reaction was then treated with 2-methyl tetrahydrofuran (2.0 mL) and aminoacetaldehyde dimethyl acetal (0.1 mL, 1.0 equivalent). The reaction was allowed to age for several hours and then solvent was removed under reduced pressure.

The resulting material was dissolved in methanol and dimethyl oxalate was added (0.3 g, 2.5 equivalents). The reaction mixture was cooled to about 0 to about 5 °C, and then sodium methoxide (0.4 mL, 30% solution in methanol, 1.75 equivalents) was introduced to the reaction slowly. After the addition was completed the reaction was heated to about 40 to about 50 °C.

After this time had elapsed, the reaction was cooled to room temperature and quenched via the addition of 2 Ν HC1 (1.5 mL). The reaction was then diluted with ethyl acetate, and the resulting phases were separated. The aqueous layer was extracted with ethyl acetate. The combined organic layers were dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The crude residue was purified via silica gel chromatography to yield F-la.

^lR NMR (400 MHz, CDC1₃): δ 10.28 (t, J= 5.5 Hz, 1H), 8.38 (s, 1H), 6.66 – 6.53 (m, 2H), 4.58 (d, J= 5.6 Hz, 2H), 4.43 (t, J= 4.7 Hz, 1H), 4.00 (d, J= 4.7 Hz, 2H), 3.92 (s, 3H), 3.88 (s, 3H), 3.32 (s, 6H). ¹³C NMR (100 MHz, CDC1₃): δ 173.08, 163.81, 162.17, 162.14 (ddd, J= 249.2, 15.6, 15.6 Hz), 161.72 (ddd, J= 250.5, 15.0, 10.9 Hz), 149.37, 144.64, 134.98, 119.21, 1 10.53 (ddd, J= 19.8, 4.7, 4.7 Hz), 102.70, 100.22 (m), 60.68, 56.75, 55.61, 53.35, 30.64. LCMS, Calculated: 458.39, Found: 459.15 (M+H).

E. Condensation of F-la with N-la to form G-la:

K₂C0₃, MeCN, 75 °C

To a reaction vessel were added F-la (202 mg, 1.0 equivalent) and acetonitrile (1.4 mL). The resulting solution was treated with glacial acetic acid (0.2 mL, 6.0 equivalents) and methane sulfonic acid (0.01 mL, 0.3 equivalents). The reaction was then heated to about 70 to about 75 °C.

After 3 hours, a solid mixture of N-la (0.128g, 1.5 equivalents) and potassium carbonate (0.2 g, 2.7 equivalents) was introduced to the reaction at about 70 to about 75 °C. After the addition was completed, the reaction was allowed to progress for at least about 1 hour.

After this time had elapsed, water (1.4 mL) and dichloromethane (1.4 mL) were introduced to the reaction. The phases were separated, and the aqueous layer was extracted with dichloromethane. The combined organic layers were dried over magnesium sulfate, then were filtered and concentrated under reduced pressure. The resulting crude material was purified via silica gel chromatography to obtain G-la.

^lR NMR (400 MHz, CDC1₃): δ 10.23 (t, J= 5.5 Hz, 1H), 8.39 (s, 1H), 6.60 (t, J= 8.1 Hz, 2H), 5.29 (dd, J= 9.5, 3.7 Hz, 2H), 4.57 (d, J= 5.4 Hz, 3H), 4.33 (dd, J = 12.8, 3.8 Hz, 1H), 4.02 – 3.87 (m, 1H), 3.94 (s, 3H), 2.06 – 1.88 (m, 4H), 1.78 (dd, J = 17.2, 7.5 Hz, 1H), 1.55 – 1.46 (m, 1H). ¹³C MR (100 MHz, CDC1₃): δ 174.53, 163.75, 162.33 (dd, J= 249.4, 15.7, 15.7 Hz), 161.86 (ddd, J= 250.4, 14.9, 10.9 Hz), 154.18, 154.15, 142.44, 129.75, 1 18.88, 1 10.58 (ddd, J= 19.8, 4.7, 4.7 Hz), 100.42 (m), 77.64, 74.40, 61.23, 54.79, 51.13, 38.31, 30.73, 29.55, 28.04. LCMS, Calculated: 463.14, Found: 464.15 (M+H).

Γ. Deprotection of G-la to form a compound of Formula la:

G-la (14 g) was suspended in acetonitrile (150 mL) and dichloromethane (150 mL). MgBr₂ (12 g) was added. The reaction was heated to 40 to 50 °C for approximately 10 min before being cooled to room temperature. The reaction was poured into 0.5M HC1 (140 mL) and the layers separated. The organic layer was washed with water (70 mL), and the organic layer was then concentrated. The crude product was purified by silica gel chromatography (100% dichloromethane up to 6% ethanol/dichloromethane) to afford la.

REFERENCES

see full gravir series at…………..http://medcheminternational.blogspot.in/p/ravir-series.html

//////////

C1CC2CC1N3C(O2)CN4C=C(C(=O)C(=C4C3=O)O)C(=O)NCC5=C(C=C(C=C5F)F)F

OR

c1c(cc(c(c1F)CNC(=O)c2cn3c(c(c2=O)O)C(=O)N4[C@H]5CC[C@H](C5)O[C@@H]4C3)F)F

BICTEGRAVIR, NEW PATENT, WO 2018005328, CONCERT PHARMA

WO2018005328) DEUTERATED BICTEGRAVIR 

CONCERT PHARMACEUTICALS, INC.

TUNG, Roger, D.; (US)

Concert CEO Roger Tung

Novel deuterated forms of bictegravir is claimed.  Gilead Sciences is developing the integrase inhibitor bictegravir as an oral tablet for the treatment of HIV-1 infection.

This invention relates to deuterated forms of bictegravir, and pharmaceutically acceptable salts thereof. In one aspect, the invention provides a compound of Formula (I) or a pharmaceutically acceptable salt thereof, wherein each of Y¹, Y², Y³, Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, Y⁸, Y⁹, Y^10a, Y^10b, Y^11a, and Y^11b is independently hydrogen or deuterium; provided that if each Y¹, Y², Y³, Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, Y⁸, Y⁹, Y^10a, Y^10b, and Y¹¹ is hydrogen, then Y^11b is deuterium.

Many current medicines suffer from poor absorption, distribution, metabolism and/or excretion (ADME) properties that prevent their wider use or limit their use in certain indications. Poor ADME properties are also a major reason for the failure of drug candidates in clinical trials. While formulation technologies and prodrug strategies can be employed in some cases to improve certain ADME properties, these approaches often fail to address the underlying ADME problems that exist for many drugs and drug candidates. One such problem is rapid metabolism that causes a number of drugs, which otherwise would be highly effective in treating a disease, to be cleared too rapidly from the body. A possible solution to rapid drug clearance is frequent or high dosing to attain a sufficiently high plasma level of drug. This, however, introduces a number of potential treatment problems such as poor patient compliance with the dosing regimen, side effects that become more acute with higher doses, and increased cost of treatment. A rapidly metabolized drug may also expose patients to undesirable toxic or reactive metabolites.

[3] Another ADME limitation that affects many medicines is the formation of toxic or biologically reactive metabolites. As a result, some patients receiving the drug may experience toxicities, or the safe dosing of such drugs may be limited such that patients receive a suboptimal amount of the active agent. In certain cases, modifying dosing intervals or formulation approaches can help to reduce clinical adverse effects, but often the formation of such undesirable metabolites is intrinsic to the metabolism of the compound.

[4] In some select cases, a metabolic inhibitor will be co-administered with a drug that is cleared too rapidly. Such is the case with the protease inhibitor class of drugs that are used to treat HIV infection. The FDA recommends that these drugs be co-dosed with ritonavir, an inhibitor of cytochrome P450 enzyme 3A4 (CYP3A4), the enzyme typically responsible for their metabolism (see Kempf, D.J. et al., Antimicrobial agents and chemotherapy, 1997, 41(3): 654-60). Ritonavir, however, causes adverse effects and adds to the pill burden for HIV patients who must already take a combination of different drugs. Similarly, the

CYP2D6 inhibitor quinidine has been added to dextromethorphan for the purpose of reducing rapid CYP2D6 metabolism of dextromethorphan in a treatment of pseudobulbar affect. Quinidine, however, has unwanted side effects that greatly limit its use in potential combination therapy (see Wang, L et al., Clinical Pharmacology and Therapeutics, 1994, 56(6 Pt 1): 659-67; and FDA label for quinidine at http://www.accessdata.fda.gov).

[5] In general, combining drugs with cytochrome P450 inhibitors is not a satisfactory strategy for decreasing drug clearance. The inhibition of a CYP enzyme’s activity can affect the metabolism and clearance of other drugs metabolized by that same enzyme. CYP inhibition can cause other drugs to accumulate in the body to toxic levels.

[6] A potentially attractive strategy for improving a drug’s metabolic properties is deuterium modification. In this approach, one attempts to slow the CYP-mediated metabolism of a drug or to reduce the formation of undesirable metabolites by replacing one or more hydrogen atoms with deuterium atoms. Deuterium is a safe, stable, non-radioactive isotope of hydrogen. Compared to hydrogen, deuterium forms stronger bonds with carbon. In select cases, the increased bond strength imparted by deuterium can positively impact the ADME properties of a drug, creating the potential for improved drug efficacy, safety, and/or tolerability. At the same time, because the size and shape of deuterium are essentially identical to those of hydrogen, replacement of hydrogen by deuterium would not be expected to affect the biochemical potency and selectivity of the drug as compared to the original chemical entity that contains only hydrogen.

[7] Over the past 35 years, the effects of deuterium substitution on the rate of metabolism have been reported for a very small percentage of approved drugs (see, e.g., Blake, MI et al, J Pharm Sci, 1975, 64:367-91; Foster, AB, Adv Drug Res 1985, 14:1-40 (“Foster”); Kushner, DJ et al, Can J Physiol Pharmacol 1999, 79-88; Fisher, MB et al, Curr Opin Drug Discov Devel, 2006, 9:101-09 (“Fisher”)). The results have been variable and unpredictable. For some compounds deuteration caused decreased metabolic clearance in vivo. For others, there was no change in metabolism. Still others demonstrated increased metabolic clearance. The variability in deuterium effects has also led experts to question or dismiss deuterium modification as a viable drug design strategy for inhibiting adverse metabolism (see Foster at p.35 and Fisher at p.101).

[8] The effects of deuterium modification on a drug’s metabolic properties are not predictable even when deuterium atoms are incorporated at known sites of metabolism. Only by actually preparing and testing a deuterated drug can one determine if and how the rate of metabolism will differ from that of its non-deuterated counterpart. See, for example, Fukuto et al. (J. Med. Chem.1991, 34, 2871-76). Many drugs have multiple sites where metabolism is possible. The site(s) where deuterium substitution is required and the extent of deuteration necessary to see an effect on metabolism, if any, will be different for each drug.

Exemplary Synthesis

[72] Deuterium-modified analogs of bictegravir can be synthesized by means known in the art of organic chemistry. For instance, using methods described in US Patent No.9,216,996 (Haolun J. et al., assigned to Gilead Sciences, Inc. and incorporated herein by reference), using deuterium-containing reagents provides the desired deuterated analogs.

[73] Such methods can be carried out utilizing corresponding deuterated and optionally, other isotope-containing reagents and/or intermediates to synthesize the compounds delineated herein, or invoking standard synthetic protocols known in the art for introducing isotopic atoms to a chemical structure.

[74] A convenient method for synthesizing compounds of Formula I is depicted in the Schemes below.

 [75] A generic scheme for the synthesis of compounds of Formula I is shown in Scheme 1 above. In a manner analogous to the procedure described in Wang, H. et al. Org. Lett.2015, 17, 564-567, aldol condensation of compound 1 with appropriately deuterated compound 2 affords enamine 3. Enamine 3 is then reacted with primary amine 4 to afford enamine 5, which then undergoes cyclization with dimethyl oxalate followed by ester hydrolysis to provide carboxylic acid 7.

[76] In a manner analogous to the procedure described in US 9,216,996, acetal deprotection of carboxylic acid 7 followed by cyclization with appropriately deuterated aminocyclopentanol 9 provides carboxylic acid intermediate 10. Amide coupling with appropriately deuterated benzylamine 11 followed by deprotection of the methyl ether ultimately affords a compound of Formula I in eight overall steps from compound 1.

[77] Use of appropriately deuterated reagents allows deuterium incorporation at the Y¹, Y², Y³, Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, Y⁸, Y⁹, Y^10a, Y^10b, Y^11a, and Y^11bpositions of a compound of Formula I or any appropriate intermediate herein, e.g., about 90%, about 95%, about 97%, about 98%, or about 99% deuterium incorporation at any Y¹, Y², Y³, Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, Y⁸, Y⁹, Y^10a, Y^10b, Y^11a, and/or Y^11b.

[78] Appropriately deuterated intermediates 2a and 2b, for use in the preparation of compounds of Formula I according to Scheme 1, may be prepared from corresponding deuterated reagents as exemplified in Scheme 2 below.

S h 2 S th i f C d 2 d 2b

[79] Synthesis of compound 2a (wherein Y³=H) by acetal formation of N,N-dimethylformamide (DMF) with dimethylsulfate has been described in Mesnard, D. et. al. J. Organomet. Chem.1989, 373, 1-10. Replacing DMF with N,N-dimethylformamide-d₁ (98-99 atom % D; commercially available from Cambridge Isotope Laboratories) in this reaction would thereby provide compound 2b (wherein Y³=D).

[80] Use of appropriately deuterated reagents allows deuterium incorporation at the Y³ position of a compound of Formula I or any appropriate intermediate herein, e.g., about 90%, about 95%, about 97%, about 98%, or about 99% deuterium incorporation at Y³.

[81] Appropriately deuterated intermediates 4a-4d, for use in the preparation of compounds of Formula I according to Scheme 1, may be prepared from corresponding deuterated reagents as exemplified in Scheme 3 below.

[82] As described in Malik, M. S. et. al. Org. Prep. Proc. Int.1991, 26, 764-766, acetaldehyde is converted to alkylhalide 14a via reaction with chlorine gas and subsequent acetal protection with CaCl₂ in methanol. As described in CN 103739506, reaction of 14a with aqueous ammonia and then sodium hydroxide provides primary amine 4a (wherein Y⁹=Y^10a=Y^10b=H). Replacing acetaldehyde with acetaldehyde-d₁, acetaldehyde-2,2,2-d₃, or acetaldehyde-d₄ (all commercially available from CDN Isotopes with 98-99 atom % D) in the sequence then provides access to compounds 4b (Y⁹=D, Y^10a=Y^10b=H), 4c (Y⁹=H,

Y^10a=Y^10b=D) and 4d (Y⁹=Y^10a=Y^10b=D) respectively (Schemes 3b-d).

[83] Use of appropriately deuterated reagents allows deuterium incorporation at the Y⁹, Y^10a, and Y^10b positions of a compound of Formula I or any appropriate intermediate herein, e.g., about 90%, about 95%, about 97%, about 98%, or about 99% deuterium incorporation at any Y⁹, Y^10a, and/or Y^10b.

[84] Appropriately deuterated intermediates 9a-9d, for use in the preparation of compounds of Formula I according to Scheme 1, may be prepared from corresponding deuterated reagents as exemplified in Scheme 4 below.

 [85] Following the procedures described by Gurjar, M. et. al. Heterocycles, 2009, 77, 909-925, meso-diacetate 16a is prepared in 2 steps from cyclopentadiene. Desymmetrization of 16a is then achieved enzymatically by treatment with Lipase as described in Specklin, S. et. al. Tet. Lett.201455, 6987-6991, providing 17a which is subsequently converted to aminocyclopentanol 9a (wherein Y^4a=Y^4b=Y^5a=Y^5b=Y⁶=Y^7a=Y^7b=Y⁸=H) via a 3 step sequence as reported in WO 2015195656.

[86] As depicted in Scheme 4b, aminocyclopentanol 9b (Y^4a=Y^4b=Y^5a=Y^5b=Y⁶=Y^7a=Y^7b= Y⁸=D) is obtained through an analogous synthetic sequence using cyclopentadiene-d₆ and performing the penultimate hydrogenation with D₂ in place of H₂. Cyclopentadiene-d₆ is prepared according to the procedure described in Cangoenuel, A. et. al. Inorg. Chem.2013, 52, 11859-11866.

[87] Alternatively, as shown in Scheme 4c, the meso-diol obtained in Scheme 4a is oxidized to the diketone following the procedure reported by Rasmusson, G.H. et. al. Org. Syn.1962, 42, 36-38. Subsequent mono-reduction with sodium borodeuteride and CeCl₃ then affords the D₁-alcohol in analogy to the method described in WO 2001044254 for the all-protio analog using sodium borohydride. Reduction of the remaining ketone using similar conditions provides the meso-D₂-diol in analogy to the method reported in Specklin, S. et. al. Tet. Lett.2014, 55, 6987-6991 for the all protio analog using sodium borohydride. The meso-D₂-diol is then converted to 9c (Y^4a=Y^4b=Y^5a=Y^5b=Y^7a=Y^7b=H, Y⁶=Y⁸=D) following the same procedures outlined in Scheme 4a.

[88] Likewise, the meso-diol obtained in Scheme 4b may be converted to 9d

(Y^4a=Y^4b=Y^5a=Y^5b=Y^7a=Y^7b=D, Y⁶=Y⁸=H) in an analogous manner as depicted in Scheme 4d. The use of deuterated solvents such as D₂O or MeOD may be considered to reduce the risk of D to H exchange for ketone containing intermediates.

[89] Use of appropriately deuterated reagents allows deuterium incorporation at the Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, and Y⁸ positions of a compound of Formula I or any appropriate intermediate herein, e.g., about 90%, about 95%, about 97%, about 98%, or about 99% deuterium incorporation at any Y^4a, Y^4b, Y^5a, Y^5b, Y⁶, Y^7a, Y^7b, and/or Y⁸.

[90] Appropriately deuterated intermediates 11a-11d, for use in the preparation of compounds of Formula I according to Scheme 1, may be prepared from corresponding deuterated reagents exemplified in Scheme 5 below.

Scheme 5. Synthesis of Benzylamines 11a-11d

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