Total Synthesis of 15-D2t- and 15-epi-15-E2t-Isoprostanes
摘要:
The first total synthesis of 15-D-2t-isoprostane is described. (-)-(9S, 15S)-15-D-2t-IsoP 1 and (+)-(11R, 15R)-15-epi-15-E-2t-IsoP 2 have been obtained in 15 steps from orthogonally protected enantiopure bicycle 3. Key features include an easy introduction of the cis side chains via ozonolysis, a highly selective enzymatic chemical differentiation of a non-meso-1,5-diol, and the use of a common synthetic intermediate allowing a stereodivergent approach to the target molecules.
Lipase B from Candida antarctica (CALB) has been selected as the most suitable enzyme to catalyze the regioselective monoacetylation of 1,5-diol isoprostane intermediate, using vinyl acetate as an acyl transfer reagent in THF. We next applied this reaction on linear 2-substituted, 2,2′-disubstituted-1,5-pentanediols, and cyclic 2,3-disubstituted-1,5-pentanediols. To rationalize the regioselectivity
stereocontrolled strategy toward the total synthesis of isoprostanes based on a bicyclic alpha,beta-epoxy ketone intermediate 6. Bicyclo[3.3.0]octene scaffold permitted stereodirection of reagents allowing stereoselective epoxidation, diastereoselective ketone reduction, and regioselective epoxide opening otherwise not accessible with a simple cyclopentene framework.
The first total synthesis of 15-D-2t-isoprostane is described. (-)-(9S, 15S)-15-D-2t-IsoP 1 and (+)-(11R, 15R)-15-epi-15-E-2t-IsoP 2 have been obtained in 15 steps from orthogonally protected enantiopure bicycle 3. Key features include an easy introduction of the cis side chains via ozonolysis, a highly selective enzymatic chemical differentiation of a non-meso-1,5-diol, and the use of a common synthetic intermediate allowing a stereodivergent approach to the target molecules.