A General, Convergent Strategy for the Construction of Indolizidine Alkaloids: Total Syntheses of (−)-Indolizidine 223AB and Alkaloid (−)-205B^†

N-Toluenesulfonyl aziridines comprise effective second electrophiles in the solvent controlled three-component linchpin union of silyl dithianes for the stereocontrolled convergent elaboration of protected 1,5-amino alcohols. This tactic, in conjunction with a one-flask sequential cyclization, constitutes an effective general strategy for the construction of indolizidine and related alkaloids, illustrated here with the total syntheses of (−)-indolizidine 223AB (1) and alkaloid (−)-205B (2).