Enantioselective Homocrotylboration of Aliphatic Aldehydes
摘要:
A practical route to optically pure syn-homocrotylation reagents is described, including highly diastereo- and enantioselective preparation of numerous syn-homocrotyl products, as well as several matched mismatched pairs. NMR experiments suggest that the active homocrotylating species is a cyclopropylcarbinyldichloroborane generated by chloride exchange from the PhBCl2 activator. Computational studies support the intermediacy of chloroboranes and suggest that homoallyl/homocrotyl transfers occur through Zimmerman-Traxler transition states.
Tandem Allylboration-Prins Reaction for the Rapid Construction of Substituted Tetrahydropyrans: Application to the Total Synthesis of (−)-Clavosolide A
作者:Alba Millán、James R. Smith、Jack L.-Y. Chen、Varinder K. Aggarwal
DOI:10.1002/anie.201511140
日期:2016.2.12
Tetrahydropyrans are common motifs in natural products and have now been constructed with high stereocontrol through a three-component allylboration-Prins reaction sequence. This methodology has been applied to a concise (13 steps) and efficient (14 % overall yield) synthesis of the macrolide (-)-clavosolide A. The synthesis also features an early stage glycosidation reaction to introduce the xylose