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[摘要]：Asymmetric dihydroxylation of the C-gamma=C-delta bonds in trans-configured alpha,beta,gamma,delta-unsaturated esters, carbonate formation, and Pd-0-catalyzed deoxygenation of C-gamma provided alpha,beta-unsaturated delta-hydroxy esters. Protection and chain-extension provided the corresponding alpha,beta-unsaturated ketones. Their asymmetric dihydroxylation in the presence of phenylboronic acid delivered dioxaborolanes. SmBr2-mediated deoxygenation of C-alpha, followed by Narasaka-Prasad and Claisen-Tishchenko reductions, respectively, selectively provided monoprotected (1,3)syn, (3,5)syn-, (1,3)syn, (3,5)anti-, (1,3)anti, (3,5)syn-, and (1,3)anti, (3,5)anti-configured 1,3,5-triols. Enones with a bulky OSiR3 group at C-delta were dihydroxylated with significantly poorer syn (vs. anti) selectivities. Dominating reagent control modulated by opposing ("mismatched case") or enhancing ("matched case") substrate control, respectively, might be responsible. |
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