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64872-77-1  NITRATE ,

64872-76-0 (free base)

Butoconazole nitrate, RS-35887-00-10-3, RS-35887, Gynomyk, Gynazole-1, Femstat

Molecular Formula: C19H17Cl3N2S
Molecular Weight: 411.78
Percent Composition: C 55.42%, H 4.16%, Cl 25.83%, N 6.80%, S 7.79%
Properties: Crystals from cyclohexane, mp 68-70.5°.
Melting point: mp 68-70.5°
Derivative Type: Nitrate
CAS Registry Number: 64872-77-1
Manufacturers’ Codes: RS-35887
Trademarks: Femstat (Syntex); Gynomyk (Cassenne)
Molecular Formula: C19H17Cl3N2S.HNO3
Molecular Weight: 474.79
Percent Composition: C 48.06%, H 3.82%, Cl 22.40%, N 8.85%, S 6.75%, O 10.11%
Properties: Colorless blades from acetone/ethyl acetate, mp 162-163°. LD50 in mice, male, female rats (mg/kg): >3200, >3200, 1720 orally; >1600, 940, 940 i.p. (Walker).
Melting point: mp 162-163°
Toxicity data: LD50 in mice, male, female rats (mg/kg): >3200, >3200, 1720 orally; >1600, 940, 940 i.p. (Walker)
Therap-Cat: Antifungal (topical).


 Butoconazole (trade names Gynazole-1, Mycelex-3) is an imidazole antifungal used in gynecology. It is administered as a vaginal cream.[1][2]
For the local treatment of vulvovaginal candidiasis (infections caused by Candida)

Brief background information

Salt ATC Formula MM CAS
G01AF15 C 19 H 17 Cl 3 N 2 S 411.78 g / mol 64872-76-0
mononitrate G01AF15 C 19 H 17 Cl 3 N 2 S ⋅ HNO 3 474.80 g / mol 64872-77-1

No Exclusivity found

Drug Name Femstat 3 (from Drugs@FDA)
Active Ingredient Butoconazole nitrate
Dosage Form Cream
Route Vaginal
Strength 2%
Market Status Over the Counter
Company Bayer
Patent No Patent Expiry
5993856 Nov 17, 2017

Laszlo Czibula, Laszlo Dobay, Eva Werkne Papp, Judit Nagyne Bagdy, Ferenc Sebok, “High Purity Butoconazole Nitrate with Specified Particle Size and a Process for the Preparation Thereof.” U.S. Patent US20080221190, issued September 11, 2008.

Systematic (IUPAC) name
Clinical data
Trade names Gynazole-1, Mycelex-3
AHFS/ monograph
MedlinePlus a682012
Pregnancy cat.
Legal status
Routes Vaginal cream
CAS number 67085-13-6 Yes
ATC code G01AF15
PubChem CID 47472
DrugBank DB00639
ChemSpider 43192 Yes
UNII 0Q771797PH Yes
KEGG D00880 
ChEBI CHEBI:3240 Yes
Chemical data
Formula C19H17Cl3N2S 
Mol. mass 411.776 g/mol


  • an antifungal agent for topical use

Classes substance

  • Eter chlorothiophenol
    • Imidazoles

Synthesis pathway

Synthesis of a)

Trade names

Country Trade name Manufacturer
France Ginomik Cassenne
USA Femstat Syntex
Ukraine Gіnofort BAT “Gideon Rіhter” Ugorschina


  • 2% vaginal cream

Reference for syn


  1. Synthesis of a)
    • Walker, KAM et al .: J. Med. Chem. (JMCMAR) 21, 840 (1978).
    • US 4,078,071 (Syntex; USA-prior. 28.7.1975).
    • DOS 2,800,755





Butoconazole nitrate (chemical name: l-[4-(4-chlorophenyl)-2-(2,6-dichloro- -phenylthio)-n-butyl]-imidazol nitrate) is a compound of the formula (I),

Figure imgf000003_0001


it belongs among the aryl-ethylimidazole compounds, has fungicidal activity and may be used for the treatment of vaginal infections caused primarily by Candida albicans. Azoles exert their antifungal effect via modifying the ergosterol synthesis of fungus cells; more particularly, imidazoles inhibit the 14α-demethylase enzyme, thereby bringing about an increased level of 14α-methyl sterols which, in turn, causes an alteration of cell membrane permeability leading to the destruction of the fungus cells (Tetrahedron: Asymmetry Vol 4, No. 7, pp. 1521-1526, 1993). The first process for the preparation of the butoconazole nitrate is a multistep synthesis disclosed in the US 4,078,071 patent specification. Here two reaction routes are given for the preparation of the key intermediate of the formula (TV) (l-[4-(4-chlorophenyl)-2-hydroxy-n- -butyl] -imidazole) .

Figure imgf000004_0001


According to one of them first an epoxy compound is prepared from an aromatic aldehyde or from an olefinic compound having a terminal double bond; then the epoxy compound is reacted with imidazole to yield the key intermediate. The aromatic aldehyde (VIII)

Figure imgf000004_0002


is treated with expensive and hazardous reagents (trimethylsulfoxonium iodide and sodium hydride) in dry dimethyl sulfoxide and the epoxide formed in the reaction is isolated after a complicated work-up. The epoxide so obtained is converted to the imidazole derivate in a time consuming reaction in the presence of dimethylformamide, then the key intermediate of the formula (IN) (l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) is isolated and purified in an additional step. From the compounds having terminal double bond (Nil)

Figure imgf000004_0003

(Nil) the epoxide is obtained via a highly explosive peracidic oxidation step and the epoxide is then converted into (l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) (IV) in a manner described above. In the other reaction route a poisoning aromatic α-halo-keto compound is used as starting material which is reacted with imidazole to give the corresponding keto-imidazole which, in turn, is reduced with a complex metal hydride – a reagent with potential hazards – to yield the key intermediate (IN). The reaction mixture is worked up in an involved manner. The synthesis way described in J. Med. Chem., 1978, Vol. 21, No. 8, pp 840-843 is as follows: l-chloro-4-chlorophenyl-2-butanol (II)

Figure imgf000005_0001

(II) is treated with the imidazole (III)

Figure imgf000005_0002


in the presence of sodium hydride reagent in dimethylformamide solvent. This substitution reaction takes a long time and gives the (l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]- imidazole) (IN) with a poor yield (51.7 %). In the next step of the butoconazole nitrate synthesis

(l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) (IN) is treated with thionyl chloride (which is at once a reagent and a solvent) at 65-70 °C to yield l-[4-(4-chlorophenyl)-2-chloro- -n-butyl] -imidazole of the formula (N).

Figure imgf000006_0001


The reaction mixture is then evaporated to dryness. The removal of the excess thionyl chloride, a highly corrosive substance, requires special equipment; the same applies to waste treatment, an operation which also involves an environmental risk. The residue is dissolved in dichloromethane, the solution is made alkaline by adding aqueous potassium carbonate solution. Phases are separated, the organic layer is washed with water, dried on magnesium sulphate and evaporated to give l-[4-(4-chlorophenyl)-2-chloro-n-butyl]-imidazole (N), as a gum. Said gum is dissolved in acetone and reacted with 2,6-dichlorothiophenol in the presence of potassium carbonate with a long reaction time. After the reaction has been finished, the inorganic salts are removed by filtration, the solvent is evaporated, and the residue is partitioned between water and ether. Butoconazole nitrate is precipitated with nitric acid from the ethereal layer. The end-product crystals in white plates from a mixture of acetone and ethyl acetate (yield: 84 %). Our aim was to provide a process by which the active agent can be prepared in high purity via reaction steps producing good yields and besides that said steps require neither solvents that are highly flammable and explosive (ether), carcinogenic (dimethylformamide) or corrosive (thionylchloride), nor reagents (e. g. sodium hydride) that are highly flammable or explosive. We have surprisingly found that when the starting material l-chloro-4-chlorophenyl-2-

-butanol (II) is reacted with the imidazole (III) in a mixture of toluene and aqueous sodium hydroxide solution in the presence of a phase transfer catalyst, the

(l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) (IN) key intermediate is obtained with short reaction time and excellent yield (95 %). Next we studied alternative solvents to replace the thionyl chloride in solvent function in the reaction step converting (l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) (IN) into (l-[4-(4-chlorophenyl)-2-chloro-n-butyl]-imidazole) (N). In the inert solvents which could be taken into account such as dichloromethane, toluene, chlorobenzene and dimethylformamide, the chlorinating reaction yielded a sticky reaction mixture which couldn’t be processed. We have surprisingly found, however that when (l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole) (IN) is dissolved in 1 ,2-dichloroethane and reacted with approximately equimolar amount of thionyl chloride reagent in the presence of catalytic amount of dimethylformamide at 30-35 °C temperature, a crystal suspension is obtained which is easy-to-stir during the whole reaction time, resulting in that chlorination proceeds completely giving l-[4-(4-chlorophenyl)-2-chloro-n-butyl]-imidazole (N) in quantitative yield. Being the compound sufficiently pure, it is not isolated, but separated by extraction and reacted directly with 2,6-dichlorothiophenol in methyl isobutyl ketone to give 1 -[4-(4-chlorophenyl)-2-(2,6-dichlorophenylthio)-n-butyl]-imidazole (VI) (butoconazole).

Figure imgf000007_0001


Example 1. Preparation of (1 4-(4-chlorophenyl)-2-hvdroxy-n-butyll-imidazole) (IV) To a solution of 56.7 g (0.26 mol) of l-chloro-4-chloroρhenyl-2-butanol (J. of Medicinal Chemistry, 1978. Nol. 21. No. 8. p. 842) in 200 ml of toluene 36.2 g (0.9 mol) of sodium hydroxide dissolved in 100 ml of water, 6.4 g (0.028 mol) of benzyltriethyammomum chloride and 35.2 g (0.51 mol) of imidazole (III) are added. The reaction mixture is heated at 93-95 °C for one hour then the temperature is returned to about 60 °C, the phases are separated and to the organic layer water (100 ml) is added. The mixture is first stirred at 22-25 °C for 1 hour then at 0-5 °C for two hours. The crystals are separated by filtration, washed with water (2 x 35 ml) of 0-5 °C to yield 74 g of wet (l-[4-(4-chloroρhenyl)-2-hydroxy-n-butyl]-imidazole) which is dried at maximum 50 °C in vacuo to give 61.6 g (95 %) of the product. Recrystallization from ethyl acetate gives 52.4 g (85 %) of dry product melting at 104-106 °C.


Example 2. Preparation of l-[4-(4-chlorophenvπ-2-(2,6-(McMorophenyl o)-n-butyl1-ϊmidazole nitrate (I) 25 g (0.1 mol) of l-[4-(4-chlorophenyl)-2-hydroxy-n-butyl]-imidazole (IN) is suspended in 1,2-dichloroethane (125 ml), to this suspension dimethylformamide (1 ml) and thionyl chloride (13.6 g; 0.11 mol) are added at 30-32 °C and the reaction mixture is kept at 35-38 °C for 1.5 hour under stirring. After the chlorination has been finished the homogenous solution is cooled to 15-18 °C, the excess of thionyl choride is decomposed with water (10 ml) then again water (80 ml) is added to the solution. After stirring at 20-22 °C for 0.5 hour the phases are separated and the organic layer is extracted with water (30 ml). To the aqueous solution methyl isobutyl ketone (250 ml) is added and the pH of the mixture is adjusted to 8.5 – 9 with 15 g (0.14 mol) of sodium carbonate dissolved in water (70 ml). The mixture is stirred at 22-25 °C for 0.5 hour, phases are separated, from the organic layer an 50 ml portion is distilled off to remove water and to the remaining solution 26.8 g (0.15 mol) of 2,6-dichloro-thiophenol and 40 g (0.29 mol) of dry potassium carbonate are added. The suspension is stirred at 105 – 108 °C under nitrogen for 3-4 hours. After the reaction has been finished the inorganic salts are removed by filtration at 22-25 °C, the filtrate is washed and clarified with activated carbon and the pH of the clear solution is adjusted to 3 – 3.5 by adding about 8 – 9 ml of 65 % nitric acid. The solution is stirred at the same temperature for 1 hour then the temperature is lowered to 8 – 12 °C. The crystals obtained are filtered and washed to give 48 g of wet l-[4-(4-chlorophenyl)-2-(2,6-dichlorophenylthio)-n-butyl]- -imidazole nitrate corresponding to 42.6 g (90 %) of dry product.


Details of the HPLC method: Type of the apparatus: Spectra System/TSP (manufacturer: Thermo Separation Products, USA) Column: LiChrospher RP-18, 250×4.0 mm ID., 5 μm (Merck, Germany, Cat. No. : 1.50983) Mobile phase: methanol : buffer = 8:2 Bujfer: 2.18 g KH2PO4 + 4.18 g K2HPO4-3H2O dissolved in 1000 ml of distilled water; MeOH (HPLC Gradient grade, Merck, Germany, Cat. No.: 1.06007.2500) KH2PO4 (p.a., Merck, Germany, Cat. No.: 1.04877.1000) K2HPO4-3H2O (p.a., Merck, Germany, Cat. No.: 1.05099.1000) Flow rate: 1.0 ml/min Temperature: 40 °C Detection: UN 229 nm Solvent for sampling: eluent Sample concentration: 1.0 mg/ml Injected volume: 10 μl Duration of analysis: 40 min Evaluation: area normalization method. Approximative retention time: 11.9 min B. Particle size: Particle size was determined by sieve analysis using an Alpine sieve operated by a jet of air.


WALKER K A M ET AL: “1-[4-(4-Chlorophenyl)-2-(2,6-dichloro phenylthio)-n-butyl]-1H-imidazole nitrate, a new potent antifungal agent” JOURNAL OF MEDICINAL CHEMISTRY, vol. 21, no. 8, August 1978 (1978-08), pages 840-843,

1- [4-(4-chlorophenyl)-2-(2,6-dichlorophenylthio)-n-b~-
tyll-lH-imidazole nitrate (I).

I as colorless blades
(9.6 g, 84%): mp 162-163 “C (foaming). Anal. (C19H18C13N303S)
C, H, N. The free base prepared by neutralization of a suspension
of 1 in ether with aqueous potassium carbonate and recrystallization
from cyclohexane had mp 68-70.5 “C (foaming).




The chlorohydrin (II) is obtained by the reaction of p-chlorobenzylmagnesium chloride (I) with epichlorohydrin (A) in ether. This is then converted to the crystalline alcohol (III) by reaction with sodium imidazole (B) in DMF. On treatment with thionyl chloride is converted to the corresponding chloro compound (IV). When (IV) is reacted with 2,6-dichloro thiophenol (C) in the presence of anhydrous potassium carbonate in acetone, the free base of butoconazole is formed. Neutralization of the free base (V) with nitric acid gives butoconazole.


  1. Seidman, L. S.; Skokos, C. K. (2005). “An evaluation of butoconazole nitrate 2% site release vaginal cream (Gynazole-1) compared to fluconazole 150 mg tablets (Diflucan) in the time to relief of symptoms in patients with vulvovaginal candidiasis”. Infectious diseases in obstetrics and gynecology 13 (4): 197–206. doi:10.1080/10647440500240615. PMC 1784583. PMID 16338779. edit
  2.  Butoconazole monograph

Literature References:

Imidazole derivative with antifungal properties. Prepn: K. A. M. Walker, US 4078071 (1978 to Syntex).


Prepn, toxicity, activity vs Candida albicans in mice: K. A. M. Walker et al., J. Med. Chem. 21, 840 (1978).


In vitro comparison with other antifungal agents: F. C. Odds et al., J. Antimicrob. Chemother. 14, 105 (1984).


Clinical trials in treatment of vulvovaginal candidiasis: W. Droegemueller et al., Obstet. Gynecol. 64, 530 (1984); J. B. Jacobson et al., Acta Obstet. Gynecol. Scand. 64, 241 (1985).


Comparison with miconazole, q.v.: C. S. Bradbeer et al., Genitourin. Med. 61, 270 (1985).

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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with AFRICURE PHARMA as ADVISOR, earlier assignment was with GLENMARK LIFE SCIENCES LTD, as CONSUlTANT, Retired from GLENMARK in Jan2022 Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 32 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri, etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him Open superstar worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international, etc in organic chemistry are some most read blogs He has hands on experience in initiation and developing novel routes for drug molecules and implementation them on commercial scale over a 32 PLUS year tenure till date Feb 2023, Around 35 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 100 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 100 Lakh plus views on dozen plus blogs, 227 countries, 7 continents, He makes himself available to all, contact him on +91 9323115463, email, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 38 lakh plus views on New Drug Approvals Blog in 227 countries...... , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc He has total of 32 International and Indian awards

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