Chirospecific Synthesis of (1S,3R)-1-Amino-3-(hydroxymethyl)cyclopentane, Precursor for Carbocyclic Nucleoside Synthesis. Dieckmann Cyclization with an α-Amino Acid

Article abstract of DOI:10.1021/jo00061a006

Carbocyclic nucleosides are important isosters of nucleosides possessing a variety of antiviral and antineoplastic activities.We report here a new method for the chirospecific synthesis of (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentane.This compound is a key precursor for the synthesis of some carbocyclic nucleosides.The method involves (1) an improved synthesis of (S)-2-aminoadipic acid; (2) Dieckmann cyclization of this α-amino acid to an aminocyclopentanone; and (3) elaboration of the latter to the target (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentane.The starting (S)-2-aminoadipic acid δ-methyl ester was prepared enantiomerically pure from (S)-aspartic acid in 51percent overall yield.Dieckmann condensation converted this amino acid to a (methoxycarbonyl)-cyclopentanone, and reduction of the ketone followed by elimination yielded (S)-3--1-(methoxycarbonyl)cyclopentene.Reduction of the double bond gave a mixture of the cis and trans diastereomers.This mixture was converted to a single diastereomer by epimerization and trapping of the cis isomer as (1S,4R)-2-(9-phenylfluoren-9-yl)-2-azabicyclo<2.2.1>heptan-3-one.Hydrolytic cleavage of the lactam followed by reduction gave (1S,3R)-1-amino-3-(hydroxymethyl)cyclopentane.