Novel synthetic routes to N-(2-amino-9H-purin-6-yl)-substituted amino acids

Reaction of N²-protected 2-amino-6-chloropurine with tert-butyl (S)-phenylalaninate, (R)- and (S)-valinates followed by deprotection affords 2-aminopurines bearing at 6-position the corresponding amino acid moieties, whose chiral centre is partially racemized.