Synthesis of Fused Cyclic Systems Containing Medium-Sized Rings through Tandem ROM-RCM of Norbornene Derivatives Embedded in a Carbohydrate Template
作者:Chanchal K. Malik、Ram Naresh Yadav、Michael G. B. Drew、Subrata Ghosh
DOI:10.1021/jo802077t
日期:2009.3.6
under Lewis acid catalysis producing the diastereoisomers 11a−d exclusively. The reversal of facialselectivity from an uncatalyzed reaction to a catalyzed one is unprecedented. The observed stereochemical dichotomy is attributed to rotation of the enone moiety along the σ bond linking the sugar moiety during formation of the chelate 13. This makes the Re-face of the enone moiety in 4a−d unhindered