Ester-imine condensations: preparation of racemic intermediates for the synthesis of the carbapenem antibiotics PS-5 and PS-6.
The lithium enolates of ethyl butyrate and ethyl isovalerate react with N-p-methoxyphenylcinnamaldimine in tetrahydrofuran (THF)-hexamethylphosphoric triamide (HMPA) to afford predominantly trans beta-lactams 9 (67%) and 20 (78%), respectively. beta-Lactam 9 was converted to PS-5 intermediate 18 in 21% overall yield (8 steps). Beta-lactam 20 was converted to PS-6 analog 28 in 22% overall yield using an eight step sequence.
D000900:Anti-Bacterial Agents / Q000138:chemical synthesis*; D002625:Chemistry, Organic; D055601:Organic Chemistry Phenomena; D011412:Propanolamines / Q000138:chemical synthesis*; D013845:Thienamycins / Q000138:chemical synthesis*
D000900:Anti-Bacterial Agents; D011412:Propanolamines; D013845:Thienamycins; C025707:PS-6; C016883:PS 5