The first example of a chiral Lewis acid-catalyzed enantioselective hetero-Diels-Alder (HDA) reaction between 1-dimethylamino-3-silyloxy-1,3-butadiene (Rawal's diene) and aldehydes is described. The cycloaddition reaction under the influence of 1 mol% of dirhodium(II) tetrakis[N-benzene-fused-phthaloyl-(S)-piperidinonate], Rh(2)(S-BPTPI)(4), proceeded cleanly and gave, after treatment with acetyl chloride
Second-Generation Synthesis of Azadirachtin: A Concise Preparation of the Propargylic Mesylate Fragment
作者:Alistair Boyer、Gemma E. Veitch、Edith Beckmann、Steven V. Ley
DOI:10.1002/anie.200805395
日期:2009.2.2
A second bite of the apple: A new and highly efficient synthesis of the propargylicmesylatefragment of azadirachtin has been accomplished (see scheme; Bn=benzyl, Ms=methanesulfonyl, PMB=para‐methoxybenzyl, TBDPS=tert‐butyldiphenylsilyl). An enantioselective catalytic hetero Diels–Alder reaction sets up the stereocenter at C15, which then controls the installation of the remaining functionality in