Wittig reaction between aldehyde (I) and bromo derivative (II) by means of triethyl phosphonoacetate and NaH in 1,2-dimethoxyethane (A) affords a mixture of isomeric acrylates (IIIa-b), which are hydrogenated over Pd/C in EtOH to yield derivative (IV). Hydrolysis of ethyl ester (IV) by means of KOH or NaOH provides carboxylic acid (V), which is then converted into N-protected derivative (VI) by first treatment with diphenylphosphoryl azide (DPPA) and Et3N in refluxing benzene, followed by reaction with refluxing t-butanol. Boc removal of (VI) with TFA in CH2Cl2 furnishes free amine (VII), which is finally alkylated with propyl bromide (VIII) by means of K2CO3 in DMF to yield the target product.

Wittig reaction between aldehyde (I) and bromo derivative (II) by means of triethyl phosphonoacetate and NaH in 1,2-dimethoxyethane (A) affords a mixture of isomeric acrylates (IIIa-b), which are hydrogenated over Pd/C in EtOH to yield derivative (IV). Hydrolysis of ethyl ester (IV) by means of KOH or NaOH provides carboxylic acid (V), which is then converted into N-protected derivative (VI) by first treatment with diphenylphosphoryl azide (DPPA) and Et3N in refluxing benzene, followed by reaction with refluxing t-butanol. Boc removal of (VI) with TFA in CH2Cl2 furnishes free amine (VII), which is finally alkylated with propyl bromide (VIII) by means of K2CO3 in DMF to yield the target product.