Stereocontrolled Synthesis of trans/cis-2,3-Disubstituted Cyclopropane-1,1-diesters and Applications in the Syntheses of Furanolignans

摘要

A new Michael addition/intramolecular alkylation sequence of (Z)-3-(2-bromo-3-arylacryloyl)oxazolidin-2-ones and malonates was developed. By a simple switch of the reaction conditions including the base promoter, solvent, and reaction temperature, both of the cis- and trans-isomers of a series of oxazolidinone-containing 2,3-disubstituted cyclo-propane-1,1-diesters could be obtained in good-to-excellent yields and with an excellent diastereoselectivity. The utility of the cyclopropane products was demonstrated in the diastereoselective syntheses of (+/-)-urinaligran and a stereoisomer of (+/-)-virgatusin involving the AlCl3-promoted [3+2] annulation with veraldehyde or piperonal as the key step.