Synthesis of 1,2-cyclopropanated sugars from glycals
作者:R. Murali、C. V. Ramana、M. Nagarajan
DOI:10.1039/c39950000217
日期:——
Syntheses of both forms of cyclopropanated sugars from glycals by (i) Simmons–Smith reaction and (ii) dichiorocarbene addition followed by dehalogenation are described.
Synthesis and Reactions of 1,2-Cyclopropanated Sugars
作者:C. V. Ramana、R. Murali、M. Nagarajan
DOI:10.1021/jo970948k
日期:1997.10.1
Diastereospecific cyclopropanation of glycals 1, 2, 3, 4, and 41 was carried out using either dihalocarbene addition or zinc-carbenoid addition to yield 1,2-cyclopropanated sugars. Dichloro- and dibromocarbenes added stereoselectively anti to the C-3 benzyloxy group, whereas (under Simmons-Smith conditions) the cyclopropanes were formed syn to the same substituent. The reactions of these 1,2-cyclopropanated sugars to provide either ring expanded glycosides or C-2-branched chain glycosides were explored. Solvolytic ring expansion of 1,2-dibromocyclopropanated sugars with K2CO3 in refluxing methanol yielded the corresponding chiral oxepins 20-22. Electrophilic ring openings of parent cyclopropanes (14 and 17 derived from glucal 1) were carried out with different electrophiles to give functionalized 2-deoxy-2-C-branched chain glycosides. The ring openings of 14 in different solvents resulted in both alpha- and beta-anomers, whereas 17 gave exclusively the alpha-anomer.
Effects of lipophilicity, protecting group and stereochemistry on the antimalarial activity of carbohydrate-derived thiochromans
作者:Gilbert K. Madumo、Paseka T. Moshapo、Henok H. Kinfe
DOI:10.1007/s00044-017-2105-5
日期:2018.3
influence of alkyl substituents on the aromatic ring of the thiophenol moiety in addition to the effect of protecting groups and stereochemistry on the sugar component of the target molecules. Results from the evaluation of the thiochromans for their antimalarial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum suggest that the presence of short chain alkyl substituents