buprenorphine

STAMFORD, Conn., Sept. 24, 2013 /PRNewswire/ — Purdue Pharma L.P. announced that the U.S. Food and Drug Administration (FDA) approved a new 15 mcg/hour dosage strength of Butrans® (buprenorphine) Transdermal System CIII, which will provide an additional titration option for healthcare professionals. Four strengths of Butrans will now be available: 5, 10, 15 and 20 mcg/hour. Purdue expects to launch Butrans 15 mcg/hour commercially in the U.S. in October 2013.

read all at

http://www.drugs.com/newdrugs/purdue-pharma-l-p-receives-fda-approval-15-mcg-hour-butrans-buprenorphine-transdermal-ciii-3909.html

Buprenorphine is a semi-synthetic opioid that is used to treat opioid addiction in higher dosages (>2 mg), to control moderate acute pain in non-opioid-tolerant individuals in lower dosages (~200 µg), and to control moderate chronic pain in dosages ranging from 20–70 µg/hour. It is available in a variety of formulations: Subutex, Suboxone, Zubsolv (buprenorphine HCl and naloxone HCl; typically used for opioid addiction), Temgesic (sublingual tablets for moderate to severe pain), Buprenex (solutions for injection often used for acute pain in primary-care settings), Norspan and Butrans (transdermal preparations used for chronic pain).

• The treatment of opiate abuse and dependence by substitution of the abused opiate with a safer, longer-acting opioid is often a successful pharmacotherapeutic intervention strategy. Heroin, a widely abused opiate, acts as an agonist for the mu-opioid receptor (MOR). Heroin is often abused using intravenous injection, often resulting in needle-sharing among addicts, which is often responsible for the spread of life-threatening infections such as hepatitis C and HIV/AIDS. Methadone has been used as a substitute MOR agonist. Methadone is orally active, and has sufficient duration of action to enable it to be given as a single daily dose. More recently, buprenorphine 1, 21-(cyclopropyl-7α-[(S)-1-hydroxy-1,2,2-trimethylpropyl]-6,14-endo-ethano-6,7,8,14-tetrahydro-oripavine, a MOR partial agonist, has been used as a pharmacotherapy (see, e.g., U.S. Pat. No. 4,935,428 ). As a partial MOR agonist, it has a lower ceiling to its MOR-mediated effects than a full MOR agonist (e.g., methadone). As a result, buprenorphine has a greater margin of safety than full MOR agonists. In addition, buprenorphine also has a long duration of action. Buprenorphine’s enhanced safety, coupled with its extended duration, enables a relatively long dosing interval, typically every 24 hours, but this can be extended to every 72 hours or more.

  

  Buprenorphine’s favorable safety profile compared to methadone has allowed it to be prescribed by office-based physicians, which has substantially decreased the cost of treatment, and increased the number of addicts in pharmacotherapy treatment.

• For the treatment of opiate abuse and dependence, buprenorphine is available as tablets formulated for sublingual administration, and is sold under the trademark Subutex^®. The daily maintenance dose for Subutex^® is in the range 4-16 mg. Subutex^®is readily soluble in aqueous media, making it possible for addicts to misuse the formulation by dissolving the tablets in water, and then injecting the resulting solution. To counter this misuse, buprenorphine has been formulated as a mixture with the MOR antagonist naloxone in a 4:1 ratio (Suboxone^®).
• Sublingual administration of buprenorphine has several drawbacks, notably the need to avoid swallowing the tablet because of buprenorphine’s low bioavailability (∼5%) when taken orally. In comparison, buprenorphine’s bioavailability is approximately fifty percent when absorbed sublingually (see, e.g., Jasinski and Preston, Buprenorphine, Ed. A Cowan, JW Lewis, Wiley-Lis, NY pp. 189-211).
• Several buprenorphine ester derivatives are described by Stinchcomb et al. in Pharm. Res (1995), 12, 1526-1529. The physiochemical properties of the esters are described, and compared with those of buprenorphine hydrochloride and its free base. Stinchcomb et al. also describe transdermal absorption of these esters in Biol. Pharm. Bull. (1996), 19, 263-267 and Pharm. Res. (1996), 13, 1519-1523. Wang, Published U.S. Patent Application No. 2005/0075361 , also describes some buprenorphine derivatives, which are apparently useful for pain relief when delivered intramuscularly or subcutaneously. EP 1 422 230 discloses buprenorphine monocarboxylic ester derivatives and dibuprenorphine dicarboxylic ester derivatives which exert a longer analgesic effect as compared to buprenorphine hydrochloride.

Buprenorphine hydrochloride was first marketed in the 1980s by Reckitt & Colman (now Reckitt Benckiser) as an analgesic, generally available as Temgesic 0.2 mg sublingual tablets, and as Buprenex in a 0.3 mg/mL injectable formulation. In October 2002, the Food and Drug Administration (FDA) of the United States also approved Suboxone and Subutex, buprenorphine’s high-dose sublingual tablet preparations indicated for detoxification and long-term replacement therapy in opioid dependency, and the drug is now used predominantly for this purpose.

In the European Union, Suboxone and Subutex, buprenorphine’s high-dose sublingual tablet preparations, were approved for opioid addiction treatment in September 2006.^[3] In the Netherlands, buprenorphine is a List II drug of the Opium Law, though special rules and guidelines apply to its prescription and dispensation. In the United States, it was rescheduled to Schedule III drug from Schedule V just before FDA approval of Suboxone and Subutex.^[4] In recent years, buprenorphine has been introduced in most European countries as a transdermal formulation for the treatment of chronic pain.

Commercial preparations

British firm Reckitt & Colman (now Reckitt Benckiser) first marketed buprenorphine under the trade names Temgesic (sublingual/parenteral preparations) and Buprenex (parenteral). Subsequently, two more formulations were released: Subutex (white, oval-shaped, bitter, no active additives) and Suboxone (white color [orange in the U.S.], hexagonal tablet, lemon-lime-flavored, one part naloxone for every four parts buprenorphine). The orange film strips form of Suboxone are lemon flavor. More than 71% of patients gave Suboxone film a favorable taste rating.^[5]

8mg Suboxone film strip

Subutex and Suboxone are available in 2 mg and 8 mg sublingual dosages. (Suboxone Film is also available in doses of 4 mg/1 mg & 12 mg/3 mg buprenorphine/naloxone respectively). On October 8, 2009, Roxane Laboratories of Columbus, Ohio, United States won FDA approval for a generic preparation of Subutex^[6] and as of October 23, 2009, announced that it is ready for distribution nationwide in 2 mg and 8 mg sublingual dosages. The demand for this generic was so high that Roxane did not produce enough to meet market demand, resulting in pharmacies running out and being unable to order more.^[7] Teva Pharmaceutical Laboratories of Tel Aviv, Israel also received approval (as of April 1, 2010) for a generic formulation of Subutex sublingual tablets in 2 mg and 8 mg dosages that are currently available in limited distribution in America as of June 20, 2010. In 2013, Reckitt Benckiser voluntarily discontinued the sale of Suboxone tablets in the United States based on data from Poison control centers that consistently found significantly higher rates (7.8–8.5 times greater) of accidental pediatric exposure with Suboxone tablets as compared with Suboxone Film.^[8]

Since 2001, buprenorphine is also available transdermally as 35, 52.5, and 70 µg/h transdermal patches that deliver the dose over 96 hours. This dosage form is marketed as Transtec in most European countries by Grunenthal (Napp Pharmaceuticals in the UK,^[9][10] Norpharma in Denmark) for the treatment of moderate to severe cancer pain and severe non-cancer pain not responding to non-opioids.

Other available buprenorphine formulations include a 5, 10, and 20 µg/h, 7-day patch, marketed as Butrans in the U.S. by Purdue Pharma (and by Napp Pharmaceuticals in the UK) indicated for the management of moderate to severe chronic pain in patients requiring a continuous, around-the-clock opioid analgesic for an extended period of time.^[11] A similar transdermal system is marketed by a collaboration between Mundipharma and Grunenthal in Australia under the name Norspan, with indications for moderate chronic pain not responding to non-opioids, dosed in 5, 10, or 20 µg/h patches.^[12]

In India: Addnok 0.4, 2 & 8 Mg Sublingual Tablets by Rusan Pharma Ltd.,^[13] Tidigesic 0.2 mg (slow release) or 0.3 mg/mL injectable by Sun Pharmaceuticals;^[14] Buprigesic (0.3 mg/mL) by Neon Laboratories;^[15] Morgesic (0.3 mg/mL) by Samarth Pharma; Norphin (0.3 mg/mL) Unichem Laboratories.

A novel implantable formulation of buprenorphine (Probuphine), using a polymer matrix sustained-release technology, has been developed to offer treatment for opioid dependence while minimizing risks of patient noncompliance and illicit diversion. FDA requested additional information about Probuphine on April 30, 2013, in a complete response letter to Titan Pharmaceuticals pending NDA.^[16]

In addition to the sublingual tablet, Suboxone is now marketed in the form of a sublingual film, available in the 2 mg/0.5 mg, 4 mg/1 mg, 8 mg/2 mg, and recently 12 mg/3 mg dosages; the film is not available in Canada or the United Kingdom (where it was discovered). The makers of Suboxone, Reckitt Benckiser, claim that the film has some advantages over the traditional tablet in that it dissolves faster and, unlike the tablet, adheres to the oral mucosa under the tongue, preventing it from being swallowed or falling out; that patients favor its taste over the tablet, stating that “more than 71% of patients scored the taste as neutral or better”; that each film strip is individually wrapped in a compact unit-dose pouch that is child-resistant and easy to carry; and that it is clinically interchangeable with the Suboxone tablet and can also be dosed once daily.^[17] Reckitt Benckiser also states that the film discourages misuse and abuse, as the paper-thin film is more difficult to crush and snort. Also, a ten-digit code is printed on each pouch, which helps facilitate medication counts and, therefore, serves to deter diversion into the illegal drug market. Although Suboxone film may deter snorting the drug it makes injecting the drug much easier as the films are extremely easy to dissolve in water making for easy injection and the fact that the naloxone in suboxone is ineffective at blocking the effects of buprenorphine when injected by addicts not dependent on another opioid.

Physicochemical properties

Buprenorphine is a semi-synthetic derivative of thebaine, one of the most chemically reactive opium alkaloids. Buprenorphine has a molecular weight of 467 and its structure is typically opioid with the inclusion of a C-7 side-chain containing a t-butyl group. This group confers overall lipophilicity on the molecule which has an important influence on its pharmacology.

Opioids exert their pharmacological effects by binding to opioid receptors. The pharmacological effects are determined by the nature of opioid-receptor interaction. Some of these effects such as analgesia, mediated by an agonistic action at the μ-opioid receptor are desirable, whereas others such as nausea, sedation, or constipation can be considered as unwanted adverse effects. Buprenorphine is a μ-opioid receptor agonist with high affinity, but low intrinsic activity. Compared with morphine (a full μ-opioid agonist) buprenorphine is considered a partial μ-opioid agonist displaying high affinity for and slow dissociation from the μ-opioid receptor. A full dose-dependent effect on analgesia has been seen within the clinically relevant dose range (up to 10 mg), but no respiratory depression which levels off at higher doses (Dahan et al. 2005). Clinically, there is also a less marked effect of buprenorphine-binding to μ-opioid receptors on gastrointestinal transit times, and indeed constipation seen in the clinic is remarkably low (Griessinger et al. 2005). Buprenorphine also shows partial agonistic activity at the opioid receptor-like receptor 1 (ORL1)-receptors which are (at least at supraspinal receptors) postulated to induce a pronociceptive effect. A study by Lutfy et al. (2003) reported that co-activation of ORL1-receptors compromises the antinociception induced by activation of the μ-opioid receptor. ORL1-activation has also an effect on hyperalgesia. It might be that buprenorphine’s partial agonism reduces this effect compared with full ORL1-agonists such as morphine or fentanyl. Buprenorphine’s antagonistic action at the δ-receptors which have a marked anti-opioid action and seem to negatively modulate central analgesia seems further to contribute to its clinically seen analgesic effect. Its likewise antagonistic activity at the κ-opioid receptors might explain the fact that it induces much less sedation and psychotomimetic effects than morphine or fentanyl (Lewis 1985; Leander 1988). Animal studies have shown that buprenorphine has a 20–40 times higher potency than morphine (Martin et al. 1976).

The strong binding of buprenorphine to the μ-opioid receptor has several consequences. Initial binding is relatively slow compared with other opioids such as fentanyl (Boas and Villiger 1985). However, the onset of analgesia is not dissimilar, since buprenorphine achieves effective analgesia at relatively low receptor occupancy (5%–10%) (Tyers 1980) and thus relatively low plasma concentrations of buprenorphine are sufficient to provide effective pain relief. The slow dissociation of buprenorphine from the receptor results in a long duration of effect and also confers another advantage in that when the drug is withdrawn an abstinence syndrome is rarely seen because of the long time taken for the drug to come off the receptor (Bickel et al. 1988).

1 Weinberg, D. S.; Inturrisi, C. E.; Reidenberg, B.; Moulin, D. E.; Nip, T. J.; Wallenstein, S.; Houde, R. W.; Foley, K. M. (1988). “Sublingual absorption of selected opioid analgesics”. Clinical pharmacology and therapeutics 44 (3): 335–342. PMID 2458208.
2. Eriksen, J.; Jensen, N. H.; Kamp-Jensen, M.; Bjarnø, H.; Friis, P.; Brewster, D. (1989). “The systemic availability of buprenorphine administered by nasal spray”. The Journal of pharmacy and pharmacology 41 (11): 803–805. PMID 2576057.
3. Suboxone EU Approval
4.DEA Rescheduling
5.What flavor do suboxone come in?. Kgbanswers.com (2012-09-06). Retrieved on 2013-05-19.
6.FDA Approval Letter to Roxane
7.Generic buprenorphine shortage
8.Reckitt Benckiser Announcement of Suboxone tablets withdrawal
9.Napp Pharmaceuticals
10.electronic Medicines Compendium (eMC) of UK medicines, Transtec product characteristics. Medicines.org.uk (2010-10-21). Retrieved on 2013-05-19.
11. “Butrans”, accessed January 23, 2011.
12. “Norspan Buprenorphine Drug/Medicine information”. news-medical.net
13.Addnok information
14. Tidigesic in India
15. Buprigesic in India
16.Probuphine complete response letter
17. Suboxone film patient information
18 Likar, R. (2006). “Transdermal buprenorphine in the management of persistent pain – safety aspects”. Therapeutics and clinical risk management 2 (1): 115–125. PMC 1661652. PMID 18360586.

• U.S. National Library of Medicine: Buprenorphine information portal
• U.S. Federal government buprenorphine program for opioid addiction
• U.S. Federal Government listing of doctors who can prescribe buprenorphine for opioid addiction
• U.S. Non-government listing of doctors who can prescribe buprenorphine for opioid addiction
• NAABT: Non-profit buprenorphine advocate
• Australian national buprenorphine policy
• The bitter pill: A Wired Magazine article on Suboxone
• Subu Must Die – How a nation of junkies went cold turkey: A New Republic article on Subutex abuse in the nation of Georgia
• Erowid.org buprenorphine page
• Methadone support.org: A methadone anonymous site
• Methdone.US: A resource center on opioid addiction treatment

• Buprenorphine acts as a mixed agonist / antagonist and it is an important treatment option for opiate addiction and analgesia.
• • Opiate compounds such as (-)-naltrexone, (-)-naloxone, (-)-nalbuphene, (-)-nalmefene, and (-)-buprenorphine have been used for addiction therapy. (-)-Buprenorphine, in particular, is increasingly being used for the treatment of heroin addiction. Recently, the (+)-opiate enantiomers have been shown to have important bioactivities that differ from their (-) counter parts. Because of the exceptional opiate medicinal activity of (-)-buprenorphine, there is great interest in the therapeutic efficacy of (+)-buprenorphine. In order to explore the possible benefits of this compound, there is a need in the art for synthetic routes to produce (+)-buprenorphine or its derivatives in an efficient and cost effective manner that generates a high yield of product having a high degree of purity.
  • The following documents disclose processes for the preparation of buprenorphine:

    • D1: WO 2007/081506 A (MALLINCKRODT INC [US]) 19 July 2007 (2007-07-19)
    • D2: J. MARTON ET AL: “Herstellung von 6,14-Ethenomorphinan-Derivaten” LIEBIGS ANNALEN DER CHEMIE, 1993, pages 915-919, XP002519987
    • D1 discloses a process for the preparation of buprenorphine from oripavine.
    • D2 discloses a process
• [0002]
  The conventional synthetic route used world-wide to prepare buprenorphine utilizes thebaine as the starting material.

  
• [0003]
  Through a series of chemical reactions, thebaine is converted into nor-buprenorphine, the immediate precursor to buprenorphine. The final step adds a cyclopropyl methyl group to the nitrogen to form buprenorphine from nor-buprenorphine.
• [0004]
  An outline of the conventional series of reactions from thebaine to buprenorphine follows:

  1. 1. Reaction of thebaine with methyl vinyl ketone to form the 4 + 2 reaction product.
  2. 2. Hydrogenation of the carbon-carbon double bond.
  3. 3. Addition of a tertiary butyl group via a Grignard Reaction.
  4. 4. An N-demethylation, via a two step reaction sequence.
  5. 5. An O-demethylation reaction and an N-cyano hydrolysis.
  6. 6. Addition of the cyclopropyl methyl group to form buprenorphine.
• [0005]
  A drawback of this conventional production scheme is that the O-demethylation step is considered a low to moderate yield transformation. There is therefore a need for a norbuprenorphine/buprenorphine production scheme that does not include an O-demethylation step.
• [0006]
  Processes for preparing Bupremorphine or Bupremorphine derivatives are disclosed in EP1439179 , US5849915 and Chem. Commun., 16, 2002, 1762-1763

• [0007]
  An aspect of the present invention is to provide a method for producing norbuprenorphine utilizing oripavine as the starting material. The method comprises:

  • reacting oripavine according to Formula I with methyl vinyl ketone to form a compound according to Formula II;
    
  • hydrogenating the compound according to Formula II to form a compound according to Formula III;
    
  • adding a t-butyl group to the compound according to Formula III to form a compound according to Formula X; and
    
  • demethylating the nitrogen of the compound according to Formula X to form norbuprenorphine, Formula VIII.
    
• [0008]
  Another aspect of the present invention is to provide a method of making buprenorphine utilizing oripavine as the starting material.

• [0009]
  There is provided a method utilizing oripavine as the preferred starting material for the synthesis of nor-buprenorphine and optionally buprenorphine. Oripavine is a naturally occurring alkaloid of Papaver somniferum. The key difference between the conventional technology and the present use of oripavine as a starting material is that the O-demethylation step, typically a low to moderate yield transformation, is not needed since the oripavine molecule lacks an O-3 methyl group. In a synthesis involving several steps, it is advantageous to have only high yield reactions, in order for the overall transformation to be economical. Since the present oripavine based synthesis does not require the O-3 demethylation step, the overall yield from oripavine provides an improved yield over that traditionally achieved when thebaine is used as the starting material. The conversion route from oripavine to produce buprenorphine is convenient and more straightforward as compared to other synthetic routes.
• [0010]
  An illustrative embodiment of the steps for converting oripavine into norbuprenorphine, and optionally buprenorphine, is as follows:

  

  
• [0011]
  The sequence outlined above is an illustrative embodiment presented to show the transformations required, but is not limited as to the order in which the transformations may be employed. In an alternative embodiment, the hydrogenation of the Diels-Alder double bond can also be accomplished as part of step 7 when the removal of the Y protecting group is through catalytic hydrogenation.

Step 1:

• [0012]
  The first step involves reaction of the oripavine with methyl vinyl ketone. This addition reaction may be accomplished by any conventional method known in the art. An illustrative embodiment is a Diels-Alder reaction in which the oripavine and methyl vinyl ketone are dissolved in a solvent and refluxed until the reaction is substantially complete. Illustrative suitable solvents include isopropyl alcohol, methanol, ethanol, toluene and mixtures thereof. The reaction mixture is then filtered to isolate the Diels-Alder adduct solids. Typical reactions result in at least about an 85% yield of at least about 98% purity.

Step 2:

• [0013]
  The second step involves the hydrogenation of the C-C double bond. In an illustrative embodiment, the Diels-Alder adduct formed in step 1 was charged to a reaction vessel with Pd/ Carbon catalyst, then dissolved in a solvent. A presently preferred solvent is methanol, but any suitable solvent may be used, including methanol, ethanol, isopropyl alcohol, acetic acid and mixtures thereof. The hydrogenation takes place under nitrogen at an elevated pressure and temperature. The temperature and pressure are selected to insure substantial completion of the reaction, as is well known in the art. An illustrative temperature range typical of this reaction is about 50-90°C, with about 60°C being preferred and an illustrative pressure range typical of this reaction is about 20-60 psi, with about 35 psi being preferred. The reaction mixture is filtered to remove the catalyst and the resulting filtrate reduced under vacuum to yield the product according to Formula III.

Step 3:

• [0014]
  Optional step 3 discloses the addition of a protecting group Y to form a compound according to Formula IV. The preferred method using oripavine as the starting material for norbuprenorphine and then buprenorphine utilizes an O-3 protecting group. However, the reaction can be accomplished without the use of the protection group, although the overall yield may be compromised. Further, the protecting group may be removed simultaneously with another step thereby eliminating one chemical step. Addition of an O-3 protecting group may minimize unwanted chemical reactions involving the unprotected phenol function at the 3-position. Illustrative suitable protecting groups include benzyl, O-t-butyl and silyl groups.
• [0015]
  In an illustrative embodiment, the reduced Diels-Alder adduct according to Formula III and ground K₂CO₃ are added (K₂CO₃ not soluble) in chloroform and benzyl bromide, heated and refluxed. After cooling to room temperature, the reaction mixture is filtered to remove the K₂CO₃. The filtrate is then reduced under vacuum and azeo dried in toluene.

Step 4:

• [0016]
  The fourth step utilizes the crude material according to Formula IV, formed in step 3. in a Grignard reaction. Under moisture free conditions and further under an inert atmosphere, t-BuMgCl is added, followed by anhydrous toluene. The solution is distilled until a pot temperature of about 100 °C is achieved, and the compound according the Formula IV is added. The reaction is quenched, and the temperature of the reaction mixture lowered. The organic and aqueous layers are separated, and the organic layer is concentrated under vacuum yielding an oily residue. The oily residue is then purified resulting in a compound according to Formula V, of up to about 93% purity.
• [0017]
  In an alternate embodiment, the t-butyl group is added using a t-butyl lithium reagent, as is well known in the art.
• [0018]
  The N-demethylation reaction may be accomplished by any suitable method known in the art. In the illustrative embodiment shown in steps 5 and 6, the methyl group is first converted into a nitrite in step 5, followed by reduction of the nitrile group in step 6.

Step 5:

• [0019]
  In an illustrative embodiment of step 5, the tertiary alcohol starting material according to Formula V is dissolved in a solvent, flushed with an inert atmosphere, and then K₂CO₃ and cyanogen bromide are added. This reaction mixture is then refluxed until the reaction is substantially complete, cooled to room temperature and filtered to remove the K₂CO₃. The reaction mixture is then extracted and the organic layers reduced and dried under vacuum. The resulting solid is purified yielding up to about 93% clean material after drying.

Step 6:

• [0020]
  In an illustrative embodiment, potassium hydroxide is dissolved in diethylene glycol and heated. The N-CN compound according to Formula VII is added and the reaction mixture heated until the reaction is substantially complete. After cooling to room temperature, distilled water is added and the resulting solid collected and dried, with up to about 100% yield.
• [0021]
  The N-demethylation may be accomplished by any method know to those skilled in the art without departing from the instant method.

Step 7:

• [0022]
  The seventh step involves the removal of the optional protecting group. In the illustrative embodiment, the Y protecting group added in step 3 is removed. In this embodiment, the secondary amine starting material may be catalytically removed by Pd/Carbon in a suitable , solvent. Suitable solvents include methanol, ethanol, isopropyl acetate and mixtures thereof. The resulting filtrate is dried under vacuum to yield norbuprenorphine. In another embodiment, the Y protecting group may be removed with an acid, such as HCl, HOAc, HF or an F anion.

Step 8:

• [0023]
  Finally the norbuprenorphine is optionally converted to buprenorphine as illustrated in step 8. In an illustrative embodiment, the norbuprenorphine is converted to buprenorphine.
• [0024]
  In an illustrative embodiment, a mixture of norbuprenorphine, a mild base, and cyclopropylmethyl bromide are heated in an oilbath at about 80-100°C until the reaction is substantially complete. The reaction mixture is then added over 5 minutes to 160ml of water, with mechanical stirring, yielding a gum. The mixture is stirred and filtered, and the filter cake is washed with water. The HPLC will show about 90% by area of desired product, and 0.2-0.5% of an N-butenyl substituted impurity. The resulting product is dried, and then boiled in alcohol, cooled, and filtered to yield buprenorphine.
• [0025]
  In the alternative, norbuprenorphine can be converted to buprenorphine by reductive amination, or by acylation followed by reduction of the amide.
• [0026]
  In an alternative embodiment, the hydrogenation step 2 is performed on the crude reaction mixture formed in step 1, thereby providing a one-pot reaction scheme for forming a compound according to Formula III.

  
• [0027]
  The oripavine, methyl vinyl ketone and isopropyl alcohol are heated under pressure. Upon cooling, a Pd-C catalyst is added, and the reaction mixture is heated under pressure until the reaction is substantially complete. The product is then solubilized and the catalyst removed by filtration. The filtrate is then concentrated under vacuum.
• [0028]
  In another alternative embodiment, illustrated below, a method for producing norbuprenorphine, and optionally buprenorphine, from oripavine, without the use of a protecting group on O-3. The individual reactions are as discussed in more detail above.
• [0029]
  The method comprises:

  1. a) reacting the oripavine according to Formula I with methyl vinyl ketone to form a compound according to Formula II;
     
  2. b) hydrogenating the compound according to Formula II to form a compound according to Formula III;
     
  3. c) adding a t-butyl group to the compound according to Formula III to form a compound according to Formula X; and
     
  4. d) demethylating the nitrogen of the compound according to Formula X to form norbuprenorphine, Formula VIII.
     

  ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

  WO 2009078986 A1

  Th invention provides processes and intermediate compounds for producing buprenorphine. In particular, the process encompasses synthetic routes for the production of buprenorphine or derivatives of buprenorphine from norhydromorphone or derivatives of norhydromorphone. While it is envisioned that the synthetic routes described herein may be utilized to produce (+/-)-buprenorphine, in an exemplary aspect of the invention, the process encompasses the production of (+)-buprenorphine or derivatives of (+)-buprenorphine.

  For purposes of illustration, Reaction Scheme 1 depicts the production of compound 8 from compound 1 in accordance with one aspect of the present invention:

  

  

  ………………………………………………………………………………………………………………………………………………………