Stereoselectivity in formation of oxacephams from 1,3-alkylidene-threitols.
The [2+2]cycloaddition of CSI to the (Z)-propenyl ethers derived from respective 1,3-methylidene- and 1,3-ethylidene-threitols, contrary to the corresponding erythritol derivatives, is characterized by a low stereoselectivity and a lack of stereospecificity. On the other hand, the alternative method of the oxacepham formation, based on the 4-vinyloxy-azetidinone, proceeds with an excellent stereoselectivity. The CD-spectroscopy offers an attractive tool for determination of the absolute configuration of the bridgehead carbon atom at the 5-oxacepham skeleton.
Borsuk
Katarzyna
K
Institute of Organic Chemistry of the Polish Academy of Sciences, Warsaw, Poland.
Grzeszczyk
Barbara
B
Szczukiewicz
Patrycja
P
Przykorska
Beata
B
Frelek
Jadwiga
J
Chmielewski
Marek
M