Stereoselective Addition of 2-Furyllithium and 2-Thiazolyllithium to Sugar Nitrones. Synthesis of Carbon-Linked Glycoglycines
摘要:
A route to epimeric carbon-linked glycoglycines that exploits the stereoselective addition of 2-lithiofuran and 2-lithiothiazole to sugar nitrones has been described. The reaction occurs with opposite diastereofacial selectivity depending on whether the free nitrone or the diethyl aluminum chloride precomplexed derivative is employed. The resulting furyl or thiazolyl hydroxylamines are dehydroxylated to amines by the action of titanium(III) chloride. From these compounds the amino acids are revealed by the oxidative cleavage of the furan ring or by the conversion of the thiazole into the formyl group and oxidation to carboxylic acid. Compounds have been prepared wherein the alpha-amino acid moiety is installed at C-4 and C-1 of furanoses (ribo, manno, xylo, and lyxo) and at C-5 and C-1 of a pyranose (galacto).
Stereoselective Addition of 2-Furyllithium and 2-Thiazolyllithium to Sugar Nitrones. Synthesis of Carbon-Linked Glycoglycines
摘要:
A route to epimeric carbon-linked glycoglycines that exploits the stereoselective addition of 2-lithiofuran and 2-lithiothiazole to sugar nitrones has been described. The reaction occurs with opposite diastereofacial selectivity depending on whether the free nitrone or the diethyl aluminum chloride precomplexed derivative is employed. The resulting furyl or thiazolyl hydroxylamines are dehydroxylated to amines by the action of titanium(III) chloride. From these compounds the amino acids are revealed by the oxidative cleavage of the furan ring or by the conversion of the thiazole into the formyl group and oxidation to carboxylic acid. Compounds have been prepared wherein the alpha-amino acid moiety is installed at C-4 and C-1 of furanoses (ribo, manno, xylo, and lyxo) and at C-5 and C-1 of a pyranose (galacto).
Determination of the absolute configuration of α-amino-2-alkylthiazoles by circular dichroism
作者:Francisco L. Merchán、Pedro Merino、Isabel Rojo、Tomás Tejero、Alessandro Dondoni
DOI:10.1016/0957-4166(95)00286-x
日期:1995.9
Correlation between absolute configuration at the alpha-centre of the thiazole ring in the title compounds and the sign of their Cotton effect (CE) in the range 217-230 nm is reported.