A Three Component Coupling Approach to a Chiral 1β-Methylcarbapenem Key Intermediate

Conjugate addition of N-benzyl-N-(R)-1-phenylethyl)amme (R)-5 to (R)-(E)-tert-butyl 5-((tert-butyldimethylsilyl)oxy)-4-methyl-2-pentenoate (10a) produced the (3S,4R)-syn-adduct 14 with essentially 100% de in 84% yield, whereas the addition of (S)-5 to 10a afforded the (3R,4R)-anti-adduct 15 with essentially 100% de in 95% yield. The syn adduct 14 was converted upon sequential treatment with lithium diisopropylamide-methylaluminum dichloride-acetaldehyde to the key intermediate 21; the diastereoisomer ratio of 21 to other diasteroisomers was 80:20. Conversion of 21 to a 1β-methylcarbapenem key intermediate 26 was carried out readily according to the known procedures.