Oxidant controlled regio- and stereodivergent azidohydroxylation of alkenes via I<sub>2</sub> catalysis
作者:P. K. Prasad、R. N. Reddi、A. Sudalai
DOI:10.1039/c5cc02374b
日期:——
A novel, I2 catalyzed regio- and stereodivergent vicinal azidohydroxylation of alkenes leading to 1,2-azidoalcohols in high yields (up to 92%) and excellent dr (up to 98%) has been developed.
Highly regioselective ring opening of epoxides using NaN3: a short and efficient synthesis of (−)-cytoxazone
作者:Joshodeep Boruwa、Jagat C. Borah、Biswajit Kalita、Nabin C. Barua
DOI:10.1016/j.tetlet.2004.07.157
日期:2004.9
A convenient and efficient synthesis of 1,2-azido alcohols has been achieved by regioselective ring opening of epoxides using NaN3 and 4 Å molecular sieves in acetonitrile. The utility of this method has been demonstrated by achieving a shortsynthesis of (−)-cytoxazone in 48% overall yield.
Synthesis of 2-Oxazolidinones from β-Lactams: Stereospecific Total Synthesis of (−)-Cytoxazone and All of Its Stereoisomers
作者:Rajesh Kumar Mishra、Cristina M. Coates、Kevin D. Revell、Edward Turos
DOI:10.1021/ol062752p
日期:2007.2.1
2-oxazolidinones are prepared in stereomerically pure form from 3-hydroxy beta-lactams by a ring-opening-cyclization isomerization process. Application of this methodology to the total synthesis of the cytokinemodulator, (-)-cytoxazone, and its three stereoisomers is demonstrated. [reaction: see text].
Racemic cytoxazone (±-5) was synthesized starting from easily available glycidic ester (±)-1 by nucleophilic epoxide ring opening, followed by 2-oxazolidinone ring construction and calcium chloride/sodium borohydride reduction of the intermediary ester (±)-4. Kinetic resolution of (±)-5 performed by acetylation with vinyl acetate catalyzed by Penicillium camemberti lipase (PcamL) afforded, on hydrolysis of acetate (-)-6, cytoxazone (-)-5 in 33% overall yield and 88.2% enantiomeric excess (ee), and its enantiomer (+)-5 (38% yield, 89.3% ee). Base-catalyzed epimerization of intermediary (±)-4 to (±)-7, and reduction and kinetic resolution with Candida antarctica lipase (CAL) led to epi-cytoxazones (-)-8 and (+)-8.