Patent EP-1302467-A2 (EP)
Inventor: KRICH SYLVIA DR
IPC: C07D277/12
Filed: 2002-09-20
Abstract: In the preparation of 2-(hetero)aryl-4-methyl-2-thiazoline-4-(S)-carboxylic acids (I) by coupling (S)- alpha -methyl-cysteine hydrochloride (II) with a nitrile (III) or alkyl imidate (III'); (II) is reacted with 0.05-2 moles of (III)/(III') at 50 degrees C to reflux temperature and pH 6.5-10 in at least one 1-4C alcohol (optionally mixed with a hydrocarbon) in presence of 1.5-3 moles of a tertiary base. <??>In the preparation of thiazoline derivatives of formula (I) by coupling (S)- alpha -methyl-cysteine hydrochloride of formula (II) with a nitrile of formula Ar-CN (III) or a corresponding 1-4C alkyl imidate (III'); (II) is reacted with 0.05-2 moles of (III)/(III') at 50 degrees C to reflux temperature and pH 6.5-10 in at least one 1-4C alcohol (optionally mixed with a hydrocarbon) in presence of 1.5-3 moles of a tertiary base. (I) Is isolated from the reaction mixture after removal of the solvent, extraction of impurities and precipitation of (I) with acid. <??>Ar = phenyl, naphthyl, thienyl, pyridyl or quinolyl (all optionally substituted by one or more of halo, OR1, benzyloxy, 1-4C alkyl or COOR1); and <??>R1 = H or 1-4C alkyl. <??>Independent claims are also included for: <??>(1) preparation of (II) involving: <??>(a) coupling an L-cysteine compound of formula (IV) with (III)/(III') (in which any OH substituents are optionally protected) in presence of 0.9-1.3 moles per mole (IV)) of base in at least one 1-4C alcohol (optionally mixed with a hydrocarbon) to give a thiazoline derivative of formula (VI); <??>(b) esterifying the product if R2 = H; <??>(c) reacting (VI; R2 = R3) with 1-3 moles of a methylating reagent in presence of 1-5 moles of base in an ether solvent at -80 to +40 degrees C to give a methylated thiazoline derivative of formula (VII); <??>(d) hydrolyzing (VII) with base to the corresponding racemic carboxylic acid of formula (VIII), where the two-phase reaction mixture obtained by addition of base is stirred at reflux temperature then cooled, followed by acidification of the aqueous phase to pH 1.5-4.5 with hydrochloric acid (HCl) so that racemic (VIII) separates as an oil; <??>(e) adding a chiral amine (as resolution base) so that the corresponding salt with (VIII) crystallizes, the chiral acid then being released by adding a water-immiscible, HCl-resistant solvent, adjusting the pH of the aqueous phase to 1-4 by addition of HCl, separating the organic phase and removing the solvent; and <??>(f) dissolving the obtained (S)-isomer of (VIII) in HCl, boiling at reflux, cooling to 0-30 degrees C, removing the precipitated cleavage product (and if necessary extracting any remaining cleavage product), spray-drying or at least partially evaporating the aqueous phase (and if necessary removing any residual water by azeotropic distillation with a suitable solvent) to give a solution or suspension of (II) and optionally an adding ether or hydrocarbon to precipitate crystalline (II); <??>(2) preparation of (II) involving: <??>(a) steps (1a)-(1c); <??>(b) lipase-catalyzed optical resolution of (VII) to give (S)-(VIII); and <??>(c) step (1f); and <??>(3) preparation of (II) involving: <??>(a) reacting L-cysteine ethyl ester hydrochloride with 2-3 equivalents of acetone in a hydrocarbon or acetone itself as solvent, optionally in presence of a tertiary amine; <??>(b) dissolving the obtained acetonide in 2-3 equivalents of formic acid, reacting with toluene or acetic anhydride, concentrating, partitioning the residue between an ester, ether or hydrocarbon and sodium bicarbonate, sodium hydroxide or potassium hydroxide solution and azeotropically drying and evaporating the organic phase; <??>(c) deprotonating the obtained ethyl 3-formyl-2,2-dimethyl-thiazoline-4-carboxylate with 1-1.5 equivalents of lithium diisopropylamide then reacting with 1-2 equivalents of methylating agent to give racemic ethyl 3-formyl-2,2,4-trimethyl-thiazoline-4-carboxylate; <??>(d) carrying out selective hydrolysis using a lipase to give 3-formyl-2,2,4-trimethyl-thiazoline-4-carboxylic acid; and <??>(e) carrying out