Lactols and their ethers undergo smooth allylation with allyltrimethylsilane in the presence of 5 mol % iodine in dichloromethane at −78 °C to afford C-allylfuranosides in good yields and with high diastereoselectivity. The use of iodine makes this method simple, convenient and practical. This is the first report on the allylation of lactols with allyltrimethylsilane using molecular iodine as a catalyst
Total Synthesis of Haterumalides NA and NC via a Chromium-Mediated Macrocyclization
作者:Jennifer M. Schomaker、Babak Borhan
DOI:10.1021/ja8043695
日期:2008.9.17
haterumalides NA and NC were accomplished via the macrocyclization of a chlorovinylidene chromium carbenoid onto a pendant aldehyde to generate the C8-C9 bond with the desired stereoisomer as the major product. Utilizing the latter chemistry enables access to both C9 hydroxylated (haterumalides NC and ND) and C9 deoxygenated forms (haterumalides NA, NB, and NE; via deoxygenation of the C9-hydroxyl).
Stereocontrolled Synthesis of a Possible Stereoisomer of Laurenidificin and a Formal Total Synthesis of (+)-Aplysiallene Featuring a Stereospecific Ring Contraction
We report a highly stereocontrolled total synthesis of one of the possible stereoisomers of laurenidificin. Highlights of the synthesis include the formation of the 2,6-dioxabicyclo[3.3.0]octane framework by a stereospecific bromolactonization−α-bromination–ring contraction sequence, followed by a stereoselective propargylation, an insertion of the Z-enyne side chain by a hydroindation/cross coupling