1-Cyclohexane Acetic Acid
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(19) & (11) EP 2 275 401 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 19.01.2011 Bulletin 2011/03 C07C 205/00 (2006.01) C07C 261/00 (2006.01) C07C 269/00 (2006.01) C07C 271/00 (2006.01) (21) Application number: 10013362.8 (22) Date of filing: 11.06.2003 (84) Designated Contracting States: • Manthati, Suresh Kumar CH IE LI Cupertino, CA 95014 (US) • Xiang, Jia-Ning (30) Priority: 11.06.2002 US 171485 Palo Alto, CA 94303 (US) • Gallop, Mark A. (62) Document number(s) of the earlier application(s) in Los Altos, CA 94022 (US) accordance with Art. 76 EPC: 03757492.8 / 1 554 237 (74) Representative: Wytenburg, Wilhelmus Johannes et al (71) Applicant: XenoPort, Inc. Mewburn Ellis LLP Santa Clara, CA 95051 (US) 33 Gutter Lane London (72) Inventors: EC2V 8AS (GB) • Raillard, Stephen P. Mountain View, CA 94040 (US) Remarks: • Zhou, Cindy X. This application was filed on 06-10-2010 as a Palo Alto, CA 94303 (US) divisional application to the application mentioned • Yao, Fenmei under INID code 62. Mountain View, CA 94040 (US) (54) Crystalline 1-{[(a-isobutanoyloxyethoxy)carbonyl]aminomethyl}-1-cyclohexane acetic acid (57) The present invention relates to crystalline 1-{[( α-isobutanoyloxyethoxy)carbonyl] aminomethyl}-1-cyclohexane acetic acid. EP 2 275 401 A1 Printed by Jouve, 75001 PARIS (FR) EP 2 275 401 A1 Description Field 5 [0001] Methods for synthesis of 1-(acyloxy)-alkyl carbamates are provided. More particularly, the synthesis of prodrugs (i.e., 1-(acyloxy)-alkyl carbamates of GABA analogs) from 1- haloalkyl carbamates of GABA analogs are described. Also described are new 1-haloalkyl carbamates of GABA analogs. Background 10 [0002] One solution to drug delivery and/or bioavailability issues in pharmaceutical development is converting known drugs to prodrugs. Typically, in a prodrug, a polar functional group (e.g., a carboxylic acid, an amino group, a hydroxyl group, etc.) is masked by a promoiety, which is labile under physiological conditions. Accordingly, prodrugs are usually transported through hydrophobic biological barriers such as membranes and typically possess superior physicochemical 15 properties than the parent drug. [0003] Pharmacologically effective prodrugs are non-toxic and are preferably selectively cleaved at the locus of drug action. Ideally, cleavage of the promoiety occurs rapidly and quantitatively with the formation of non-toxic by-products (i.e., the hydrolyzed promoiety). [0004] The acyloxyalkoxycarbonyl functionality is an example of a promoiety that may be used to modulate the phys- 20 iochemical properties of pharmaceuticals (Alexander, United States Patent No. 4,916,230; Alexander, United States Patent No. 5,733,907; Alexander et al., U.S. Patent No. 4,426,391). Typically, 1-(acyloxy)-alkyl derivatives of a phar- maceutical possess superior bioavailability, may be less irritating to topical and gastric mucosal membranes and are usually more permeable through such membranes when compared to the parent drug. [0005] However, although 1-(acyloxy)-alkyl ester derivatives of alcohols and 1-(acyloxy)-alkyl carbamate derivatives 25 of amines have been frequently used to mask these polar functional groups in pharmaceuticals, existing synthetic methods for preparing these desirable derivatives are inadequate. Methods disclosed in the art for synthesis of acyloxy- alkyl esters and carbamates are typically multi-step routes that utilize unstable intermediates and/or toxic compounds or salts and accordingly are difficult to perform on large scale (Alexander, United States Patent No. 4,760,057; Lund, United States Patent No. 5,401,868; Alexander, United States Patent No. 4,760,057; Saariet al., European Patent 30 0416689B1). [0006] Accordingly, there is a need for a new synthesis of 1-(acyloxy)-alkyl derivatives that proceeds rapidly and efficiently, which is amenable to scale-up and proceeds through readily accessible synthetic precursors. Summary 35 [0007] A method for synthesizing 1-(acyloxy)-alkyl derivatives from acyloxy derivatives, which typically proceeds in high yield, does not necessarily require the use of heavy metals and is readily amenable to scale- up is provided herein. [0008] In a first aspect, a method of synthesizing a compound of Formula (I) is provided which comprises 40 45 50 55 2 EP 2 275 401 A1 5 contacting a compound of Formula (II), a compound of Formula ( III) and at least one equivalent of a metal salt wherein: 10 X is F, Cl, Br or I; n is 0 or 1; R1 is acyl, substituted acyl, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, 15 substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl; R2 and R3 are independently hydrogen, alkyl, substituted alkyl, alkoxycarbonyl, substituted alkoxycarbonyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, carbamoyl, substituted carbamoyl, cycloalkyl, substituted cycloalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl, or optionally, R2 and R3 together with the atom to which they are bonded form a cycloalkyl, substituted cycloalkyl, 20 cycloheteroalkyl or substituted cycloheteroalkyl ring; R4 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl; R5 is hydrogen, alkyl, substituted alkyl, alkoxy, substituted alkoxy, acyl, substituted acyl, alkoxycarbonyl, substituted 25 alkoxycarbonyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, carbamoyl, substituted carbamoyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl, or optionally, R 4 and R 5 together with the atoms to which they are attached form a cycloheteroalkyl or substituted cycloheteroalkyl ring; R6 and R 9 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted 30 aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl and substituted heteroarylalkyl; R7 and R 8 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, acyl, substituted acyl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroarylalkyl and substituted heteroarylalkyl, or optionally, R 7 and R 8 together with the carbon atom to which they 35 are attached form a cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl or bridged cy- cloalkyl ring; and R10 is hydrogen, alkyl,substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, aryldialkylsilyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl, substituted heteroarylalkyl or trialkylsilyl. 40 [0009] In a second aspect a method of synthesizing a compound of Formula (I) is provided which comprises 45 50 55 3 EP 2 275 401 A1 5 10 15 contacting a compound of Formula (II), a compound of Formula (III) and at least one equivalent of an organic base, 20 where X, n, R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 are as defined, supra. [0010] In a third aspect a compound of Formula (II) is provided, 25 30 wherein: 35 X is F, Cl, Br or I; n is 0 or 1; R2 and R3 are independently hydrogen, alkyl, substituted alkyl, alkoxycarbonyl, substituted alkoxycarbonyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, carbamoyl, substituted carbamoyl, cycloalkyl, substituted cycloalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl, 40 or optionally, R2 and R3 together with the atom to which they are bonded form a cycloalkyl, substituted cycloalkyl, cycloheteroalkyl or substituted cycloheteroalkyl ring; R4 is hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl; heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl; 45 R5 is hydrogen, alkyl, substituted alkyl, alkoxy, substituted alkoxy, acyl, substituted acyl, alkoxycarbonyl, substituted alkoxycarbonyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, carbamoyl, substituted carbamoyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroalkyl, substituted heteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl or substituted heteroarylalkyl, or optionally, R 4 and R 5 together with the atoms to which they are attached form a cycloheteroalkyl or substituted cycloheteroalkyl ring; 50 R6 and R 9 are independently selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, substituted arylalkyl, cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, substituted cycloheteroalkyl, heteroaryl, substituted heteroaryl, heteroarylalkyl and substituted