Studies in stereoselective [2+2]-cycloadditions with dichloroketene
作者:David I. MaGee、Tammy C. Mallais、Peter D.M. Mayo、George M. Strunz
DOI:10.1016/j.tet.2006.02.014
日期:2006.4
During the investigation of the reaction of dichloroketene with cyclic enoxy-lactones and acyclic enoxy-ester substrates it was found that only the acylic variants effectively participated in the [2+2]-cycloaddition. Although a complete understanding of the reasons for this are lacking, molecular mechanics calculations do suggest that an out of plane twist of the cabonyl group in the acyclic compounds
Practical Racemic and Asymmetric Formal Total Syntheses of the Homocamptothecin Derivative and Anticancer Agent Diflomotecan via Tertiary Homoallylic Alcohols as Masked Aldol Equivalents
scalable racemic as well as an asymmetric approach to the key building block for the synthesis of homocamptothecin and derivatives thereof such as the potent anticancer agent diflomotecan (4) are described. In the asymmetric route, the pyridone ring was assembled applying straightforward carbonyl chemistry. The selective generation of the quaternary stereocenter was accomplished by self reproduction of chiral