合成路线1

Substitution on dibromobutene (I) by potassium phthalimide (II) provided bromobutenyl phthalimide (III). Further treatment with sodium acetate afforded acetate (IV) which, after hydrolysis, gave phthalimidobutenol (V). Reaction with refluxing ethyl orthoacetate in the presence of a trace of butyric acid generated the intermediate ketene acetal (VI), which experienced a Claisen rearrangement to give pentenoate ester (VII). Ozonolysis of the olefinic double bond of (VII) yielded aldehyde (VIII). Then, Wittig reaction of aldehyde (VIII) with (isopropylidene)triphenylphosphorane in cold THF provided olefin (IX), which was hydrogenated in the presence of Pd/C to give the isobutyl compound (X). Finally, hydrolysis of both ester and phthalimide groups in refluxing 6 N HCl provided the GABA analogue.