[4 + 2]-Annulations of Chiral Organosilanes: Application to the Total Synthesis of Leucascandrolide A
作者:Qibin Su、Les A. Dakin、James S. Panek
DOI:10.1021/jo0610412
日期:2007.1.1
Complete details of an asymmetric synthesis of leucascandrolide A (1) are described. The synthesis highlights the use of two diastereoselective [4 + 2]-annulations for the assembly of the functionalized bispyranyl macrolide 3. An efficient assembly and union of the oxazole-containing side chain 4 with macrolide 3 was carried out using a Mitsunobu reaction. A convergent route to the oxazole side chain
Advantageous Syntheses of Diazo Compounds by Oxidation of Hydrazones with Lead Tetraacetate in Basic Environments
作者:Terrence L. Holton、Harold Schechter
DOI:10.1021/jo00120a013
日期:1995.7
Varied sensitive diazo compounds 3 are produced efficiently and safely in 3-6 g quantities by oxidation (eq 1) of hydrazones 1 at -78 degrees C with lead tetraacetate (2) in triethylamine/chloroform, N-methylmorpholine/dimethylformamide, tetramethylguanidine (8)/dimethylformamide, and tetramethylguanidine/methylene chloride, respectively, upon use of appropriate workup and handling techniques. New and improved nonhazardous procedures have been developed for preparing and handling hydrazones 1 from aldehydes and ketones in reactions with excess hydrazine.