A new totalsynthesis of forskolin 1 has been achieved and this note describes the synthesis of the trans fused enone 18 as a key-intermediate. Key steps are: 1) the intramolecular Diels-Alder reaction of 7 to afford the tricyclic lactone 8 (48–56%); 2) a stereospecific and regiospecific one-pot conversion of 11A into 12 (94%) with LiBH4/BF3-THF at room temperature. The scheme allows a very early stereospecific
作者:Richard P Hsung、Kevin P Cole、Luke R Zehnder、Jiashi Wang、Lin-Li Wei、Xiao-Fang Yang、Heather A Coverdale
DOI:10.1016/s0040-4020(02)01524-7
日期:2003.1
A 20-step total synthesis of (±)-arisugacin A with an overall yield of 2.1% is described here in detail. This synthesis features a formal [3+3] cycloaddition reaction of α,β-unsaturated iminium salts with 6-aryl-4-hydroxy-2-pyrones through a highly stereoselective 6π-electron electrocyclic ring-closure of 1-oxatriene. A strategic dihydroxylation–deoxygenation protocol leading to the desired angular