Stereochemistry of substituted isoxazolidines derived from N-methyl C-diethoxyphosphorylated nitrone
摘要:
Cycloadditions of N-methyl-C-(diethoxyphosphoryl)nitrone 1a to cyclic alkenes proceeded regio- and diastereospecifically. Reactions of la with 1, 1-disubstituted alkenes led to the regiospecific formation of 5,5-disubstituted isoxazolidines 7/8 in nearly equimolar ratios, whereas additions to trans- 1,2-disubstituted alkenes gave four isomeric isoxazolidines with up to 80% regioselectivity and moderate (up to 60%) diastereoselectivity. Stereochemistry of the substituted isoxazolidines was established based on the conformational analysis using vicinal H-H, H-P and P-C couplings, and was, in some cases, supported by geminal H-C-P=O coupling and deshielding P=O and C=O effects. (c) 2006 Elsevier Ltd. All rights reserved.
Stereochemistry of substituted isoxazolidines derived from N-methyl C-diethoxyphosphorylated nitrone
作者:Dorota G. Piotrowska
DOI:10.1016/j.tet.2006.10.011
日期:2006.12
Cycloadditions of N-methyl-C-(diethoxyphosphoryl)nitrone 1a to cyclic alkenes proceeded regio- and diastereospecifically. Reactions of la with 1, 1-disubstituted alkenes led to the regiospecific formation of 5,5-disubstituted isoxazolidines 7/8 in nearly equimolar ratios, whereas additions to trans- 1,2-disubstituted alkenes gave four isomeric isoxazolidines with up to 80% regioselectivity and moderate (up to 60%) diastereoselectivity. Stereochemistry of the substituted isoxazolidines was established based on the conformational analysis using vicinal H-H, H-P and P-C couplings, and was, in some cases, supported by geminal H-C-P=O coupling and deshielding P=O and C=O effects. (c) 2006 Elsevier Ltd. All rights reserved.
Design, synthesis and cytotoxicity of a new series of isoxazolidines derived from substituted chalcones
作者:Dorota G. Piotrowska、Marcin Cieślak、Karolina Królewska、Andrzej E. Wróblewski
DOI:10.1016/j.ejmech.2011.01.067
日期:2011.4
A new series of isomeric isoxazolidin-3-yl-3-phosphonates were synthesised from N-methyl-C-diethoxyphosphorylnitrone and substituted chalcones. The respective isoxazolidin-3-yl-3-phosphonic acids were obtained from phosphonates via dealkylation procedure using trimethylsilyl bromide. Selected phosphonates and their respective phosphonic acids were screened for their cytotoxic activity to HeLa and K562