DOUBLE DIASTEREOSELECTIVE GLUCOSIDATION OF CYCLIC HEMIACETALS - SYNTHESIS OF THE 1,4-BENZOXAZINONE ACETAL GLUCOSIDES GDIBOA AND GDIMBOA FROM GRAMINEAE

A double diastereoselective glucosidation procedure giving rise in one step to the natural (2R)-2-beta-configuration of 6 and for the first time, 7, benzoxazinoid acetal glucosides from Gramineae species, is de scribed by reaction of O-(2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl ) trichloroacetimidate 3 as glucosyl donor with 2,4-dihydroxy-2H-1,4-b enzoxazin-3(4H)-one 1 or its 7-methoxy derivative 2 as hemiacetalic gl ucosyl accepters in the presence of excess borontrifluoride etherate a s promoter without a need for a covalent protection of the cyclic hydr oxamic acid unit in the aglucones. Copyright (C) 1996 Elsevier Science Ltd