Synthesis and “anomerization” of C-glycosyl compounds related to some heterocyclic natural products
作者:King Mo Sun、Robert D. Dawe、Bert Fraser-Reid
DOI:10.1016/s0008-6215(00)90877-2
日期:1987.12
2,3- O -isopropylidene- d -ribofuranose ( 13 ) with the stabilizedWittigreagents Ph 3 PC(Me)CO 2 Me ( 14 ) and Ph 3 PC(Me)CN ( 15 ) gave olefinic products which, upon treatment with dilute base, afforded the corresponding anhydro sugars having the β- d -anomer configuration exclusively. Treatment of these kinetic products with a strong base did not affect the ester obtained from 14 , but the nitrile
C-Glycosides by Aqueous Condensation of β-Dicarbonyl Compounds with Unprotected Sugars
作者:I. Riemann、W.-D. Fessner、M. A. Papadopoulos、M. Knorst
DOI:10.1071/ch02012
日期:——
water, under mildly alkaline conditions, provides a�convenient and effective route to C-glycosidic ketones in high yields. Reactions usually proceed with high β`anomeric' stereoselectivity because product composition is determined by thermodynamic control. Mechanistically, the condensation follows a typical Knoevenagel scheme, after which an intramolecular oxa-Michael cyclization determines C-glycoside