摘要:
Asymmetric synthesis of 11, the precursor to chiral (3R,4R)-3-[(1R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-4-acetoxyazetidin-2-one (3) was achieved by utilizing a highly diastereoselective aldol-type reaction of acetaldehyde and the chiral tin(II) enolate of 5. Similar diastereoselective alkylations of chiral and achiral tin(II) enolates 13a-d with chiral 3 were also performed to obtain the desired alkylated azetidin-2-ones (17a-d). Compounds 17a,b were successfully converted to new, non-natural 1-beta-methylcarbapenems 1a and 1b, which exhibited strong and wide-ranging antimicrobial activities and excellent stability against human renal dehydropeptidase-I.