Cyclopropanations glucose chiral auxiliary

SCHEME 10.1 Cyclopropanations using glucose as a chiral auxiliary. 

Tri-O-benzyl-D-glucose is an efficient and practical chiral auxiliary. If allylic alcohols are fixed as /3-glycosides they can be cyclopropanated by an excess of the diiodomethane/diethyl-zinc reagent with excellent diastereoselectivities. Since the removal of the auxiliary proceeds under mild conditions, this method allows the synthesis of a variety of cyclopropane carbinols in very high enantiomeric excesses96. 

The diastereoselective hydroxyl-directed cyclopropanation shown in Scheme 22 was one of a number studied which proceed with high stereoselectivity. The chiral auxiliary could be removed as indicated, and use of the equivalent derivative of 6-deoxy-L-glucose gave the enantiomeric cyclopropylmethanols.l 13... 

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