Oxazoline N-oxide mediated [3+2] cycloadditions: Application to a formal synthesis of a (+)-beta-methylcarbapenem

[3+2] Cycloaddition between a camphor-derived oxazoline N-oxide 9 and the g amma,delta-unsaturated enamino ester 11 afforded the single adduct 6, A ste reoselective reduction of the enamine ester side chain allowed the control of the absolute configuration of the two additional asymmetric centres. Nit rogen protection and oxidative hydrolysis of the resulting product 13, foll owed by further functional group manipulations, led to the p-lactam derivat ive 1, a known precursor of the beta-methylthienamycin derivative 2a.