221190-07-4Relevant academic research and scientific papers
The First Total Syntheses of Enantiomerically Pure Naturally Occuring Ellagitannins Gemin D and its Regioisomer Hippomanin A
Khanbabaee, Karamali,Loetzerich, Kerstin,Borges, Markus,Grosser, Mathias
, p. 159 - 166 (2007/10/03)
The total syntheses of naturally occuring ellagitannins gemin D (1) and its regioisomer hippomanin A (2) are reported. In addition, the phase-transfer catalyzed benzylation reaction of the 2,3-glucopyranoside diols 3-7 is described. Our studies have illustrated the influence of the structure of 2,3-glucopyranoside diols on the regioselectivity of the phase-transfer catalyzed benzylation at their free 2,3-OH groups. We could show, that both phase-transfer catalyzed benzylations of 2,3-glucopyranoside diols using tetrabutylammonium hydrogensulfate (Bu4NHSO4) or using tetrabutylammonium iodide (Bu4NI) disfavour the formation of the corresponding 3-O-monobenzylated products and preferentially give the 2-O-monobenzylated products. However, the ratio of the generated 2- versus 3-O-mono- and 2,3-dibenzylated products from these reactions also strongly depends upon the nature of the starting materials. The glucopyranosides 3 and 4 are the first examples, which allow the completely regioselective monobenzylation at the 2-OH positions by a phase-transfer catalyzed reaction.
