摘要 : Chiral 10 to 12-membered nitrogen and oxygen heterocycles fused to isoxazoline rings have been prepared in a highly regioselective and stereoselective manner by intramolecular nitrile oxide cycloaddition of tethered N- and O-allyl... 展开 Chiral 10 to 12-membered nitrogen and oxygen heterocycles fused to isoxazoline rings have been prepared in a highly regioselective and stereoselective manner by intramolecular nitrile oxide cycloaddition of tethered N- and O-allyl carbohydrate derivatives. The use of a -Y-Ar-CH2 tether containing a 1,2-disubstituted aromatic ring between the heteroatom attached to the nitrile oxide-bearing carbohydrate scaffold, and the allyl group, facilitates the formation of the medium-sized rings. The cycloaddition afforded bridged isoxazolines in the cases of O-tethered allyl carbohydrate derivatives, whereas a fused isoxazoline resulted when a N(Ts)-tethered allyl derivative was used. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 17] 收起