A general method of transforming aldehydes via $ alpha$,$ beta$-unsaturated esters to the 3-substituted glutarimide ring was developed and was applied to the construction of ring A of $(-)$-sesbanimide A (1) and the AB ring moiety of (+)-sesbanimide A (2). The phase-transfer-catalyzed methylenation reaction of dihydroxy dithioacetal 46 brought about a 1,4-migration of the t -butyldiphenylsilyl group to provide 1,3-dioxolane derivative 49. / Model studies towards the synthesis of (+)-sesbanimide (2) and C-15 desmethyl sesbanimide 93 were carried out using allylsilanes 74, 79 and 94, with aldehydes 56a and 85. / The synthesis of 8- O -benzyl-13- O-t -butyldimethylsilyl sesbanimides 88, 13-deoxychloro sesbanimide 89, 8- O -benzyl-13- O - t -butyldimethylsilyl-15-desmethyl sesbanimide 91, 13-deoxychloro-15-desmethyl sesbanimide 92, 8- O -benzyl-13- O - t -butyldiphenylsilyl-15-desmethyl sesbanimide 96 and 13- O - t -butyldiphenylsilyl-15-desmethyl sesbanimide 97 are described.

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