Abstract: An improved process for preparing .alpha.,.omega.-diamino acids, such as D,L-homolysine, 2,8-diaminooctanoic acid, ornithine, lysine, or the like, comprising reaction of phthalic anhydride and an amino alcohol in a hydrocarbon solvent; treatment of the resulting phthalimide--N--(CH.sub.2).sub.n --OH derivative, without isolation thereof, with phosphorus tribromide or phosphorous pentachloride; alkylation of diethyl acetamidomalonate with the phthalimide--N--(CH.sub.2).sub.n --chloride or --bromide of the previous step, in the presence of, particularly, sodium hydride/dimethylformamide; standard acid hydrolysis and decarboxylation; selective protection via copper(II) chelation, N-specific acylation with benzyl chloroformate, and decomposition of the amino acid-copper(II) complex with alkaline thioacetamide; standard t-butoxycarbonyl acylation; and deprotection to obtain the desired .alpha.,.omega.-diamino acids.