RESUMO
Specific deuterated reference compounds were prepared to probe the stereoselectivity of the reductive ring opening of carbohydrate-based benzylidene-type acetals. AlD(3) revealed a retentive stereoselectivity probably through the rare S(N)i (internal nucleophilic substitution) mechanism. An S(N)1-like mechanism occurs in the acid-promoted regioselective BD(3)·THF- or Et(3)SiD-reductive ring opening.
Assuntos
Acetais/química , Compostos de Benzilideno/química , Química Orgânica/métodos , Deutério/química , Compostos de Alumínio/química , Glicosilação , Hidróxidos/química , Compostos de Lítio/química , Espectroscopia de Ressonância Magnética , Oxirredução , EstereoisomerismoRESUMO
[Structure: see text] An efficient synthesis of the entire set of suitably protected 48 disaccharide building blocks for the assembly of a heparin and heparan sulfate oligosaccharide library is described here.
Assuntos
Dissacarídeos/síntese química , Heparina/química , Heparitina Sulfato/química , Sequência de CarboidratosAssuntos
Acetais/química , Compostos de Benzilideno/química , Cobre/química , Catálise , OxirreduçãoRESUMO
[reaction: see text] A highly regioselective borane-reductive ring opening of the 4,6-O-benzylidene-D-hexopyranosides to the corresponding 6-alcohols in excellent yields at room temperature via various metal trifluoromethanesulfonates as catalysts is described here. Its application in the synthesis of 1,4-dideoxy-1,4-imino-L-xylitol is also highlighted.
