Asymmetric synthesis of the carbocyclic nucleoside building block (R)-(+)-4-aminocyclopentenone using delta-amino beta-ketophosphonates and ring-closing metathesis (RCM).

Amino keto-2,7-dienes undergo ring-closing metathesis (RCM) to give 4-aminocyclopentenones, valuable intermediates in the asymmetric construction of carbocyclic nucleosides. The key amino ketodienes were prepared using delta-amino beta-ketophophonates, a new sulfinimine-derived chiral building block, and HWE chemistry. [reaction: see text]