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. Author manuscript; available in PMC: 2017 Aug 8.
Published in final edited form as: Org Lett. 2012 Feb 24;14(6):1394–1397. doi: 10.1021/ol300105q

Scheme 1. Rh2(Esp)2-Catalyzed Cyclopropanations of Natural Products Bearing Electron-Rich Alkenes with Alkynyl Diazo Ester 2d.a.

Scheme 1

aDiastereomeric ratios were determined by 1H NMR (500 MHz); the relative stereochemistry of the major diastereomers was not determined since in some cases they were inseparable (see Supporting Information). b3.0 equiv of diazo ester 2d were employed. cSilylation was performed prior to cyclopropanation (TMSCl, DMAP, Et3N, CH2Cl2, 22 °C).