合成路线1

4) The deamination of L-leucine (XXIV) with NaNO2, NaBr and H2SO4 gives 2(S)-bromo-4-methylpentanoic acid (XXV), which is esterified with tert-butyl acetate and BF3.AcOH to yield the tert-butyl ester (XXVI). The condensation of (XXVI) with the sodium salt of diethyl malonate affords the substituted malonic ester (XXVII), which is selectively hydrolyzed at the tert-butyl ester group with formic acid, giving the monoacid (XXVIII). The decarboxylative reduction of (XXVIII) with BH3 and SMe2 provides 3(S)-isobutylbutano-4-lactone (XXIX). Lactone (XXIX) is submitted to ring opening by treatment with trimethylsilyl iodide in ethanol, yielding 3(S)-(iodomethyl)-5-methylhexanoic acid ethyl ester (XXX). The reaction of (XXX) with sodium azide yields azide (XXXI), which is hydrolyzed with KOH in ethanol/water to afford the free acid (XVII). Finally, this compound is reduced to pregabalin by treatment with H2 over Pd/C.