alpha alpha-Disubstituted piperidines and conformationally constrained polyhydroxylated indolizidines bearing a hydroxymethyl substituent in position 8a were synthesized from a readily available L-sorbose-derived ketonitrone. Diastereoselective vinylation under two sets of complementary conditions allowed access to both configurations of the newly formed quaternary stereocenter. Subsequent N-allylation and ring-closing metathesis afforded 8a-branched indolizidines in high yield. The newly prepared iminosugars demonstrated highly potent inhibition of alpha-glucosidases. Most interestingly, compound 9b exhibits very high selectivity toward this class of enzymes, with an unusual mode of binding.
Magnesium-mediated Wittig reagent-promoted Stereoselective synthesis of L-Sorbopyranoses from D-Glucopyranoses
作者:Karim Ullah、Ming Li、Yubin Zheng、Wangze Song
DOI:10.1016/j.carres.2021.108257
日期:2021.3
rare sugar that exists in some natural products and widely used in pharmaceutical and chemical industries. Herein, two simple and practical routes were developed using cheap magnesium (II) for the synthesis of 1,3,4,5-tetra-O-benzyl-l-sorbopyranose from 2,3,4,6-tetra-O-benzyl-d-glucopyranose with high stereoselectivity and yield. The first route involved the intramolecular hydride shift from C5 to
The bromomagnesium salts of certain alcohols and phenols in dichloromethane cleanly promote the title transformation; the reaction proceds via formal hydride transfer from C-5 to anomeric carbon of the glucopyranose precursor.