Organometallics in organic synthesis. Applications of a new diorganozinc reaction to the synthesis of C-glycosyl compounds with evidence for an oxonium-ion mechanism
作者:Alan P. Kozikowski、Toshiro Konoke、Allen Ritter
DOI:10.1016/s0008-6215(00)90882-6
日期:1987.12
features of a new organozinc-based substitution process [heteroatom-C-(R1,R2)-SPh + R3(2)Zn----heteroatom-C-(R1,R2,R3)], first discovered during a total synthesis of the alkaloid mycotoxin alpha-cyclopiazonic acid, are described. Phenyl thioglycosides were valuable substrates in studying the nature of this reaction process. Since these sulfur compounds are converted into C-glycosylcompounds with some
An Efficient Synthesis of β-<i>C</i>-Glycosides Based on the Conformational Restriction Strategy: Lewis Acid Promoted Silane Reduction of the Anomeric Position with Complete Stereoselectivity
[reaction: see text] The reduction of glyconolactols having an anomeric carbon substituent by Et(3)SiH/TMSOTf proceeded with complete stereoselectivity to produce the corresponding beta-C-glycosides when the substrates were conformationally restricted in the (4)C(1)-chair form by a 3,4-O-cyclic diketal or a 4,6-O-benzylidene protecting group. Thus, the efficient construction of beta-C-glycosides was
for regioselectivedeacetylation at sugar 3-OH of peracetylated 6-deoxy-C-glucopyranosides mediated by BCl3 was developed. The approach could be extended to other sugar-derived 6-deoxy-C-glycopyranosides, such as those derived from mannose, galactose, and rhamnose, with deacetylation occurring at varied sugar hydroxyl groups, and further extended to 4-deoxy-C-glucopyranosides with deacetylation occurring