Asymmetric synthesis of an important precursor to 5′-nor carbocyclic nucleosides

An asymmetric hetero-Diels-Alder reaction involving an amino acid-derived acylnitroso dienophile was utilized to synthesize (1S, 4R)-4-[N-(tert-butoxycarbonyl)amino]-2-cyclopentene-1-ol (4). The amino acid chiral auxiliary was removed by the Edman degradation. This enantiomerically pure aminoalcohol is a key intermediate in the synthesis of 5′-nor carbocyclic nucleosides.