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Research describes a versatile pyridinium salt photoelectrocyclization/aziridine ring cleavage sequence methodology for the synthesis of mannostatin analogues, (+)-4-epimannostatin and (+)-mannostatin A regioisomers.

The photochemistry of selected N-silylalkyl-substituted phthalimides and maleimides is examined to analyze the generality and preparative consequences of a solvent effect on excited-state reaction chemoselectivities and quantum efficiencies. This solvent effect is observed in the photochemistry of N-((trimethylsilyl)butyl)phthalimide 10 and in the photochemistry of the N-silylpropyl-maleimide. The results show the generality of the solvent effect and how it can be applied to improve the preparative utility of the photochemistry of N-(silylalkyl)phthalimides and N-(silylalkyl)maleimides.

The C to O silyl migration occurs in the photochemical reactions of N-trimethylsilylmethyl imides which form azomethine ylide and this pathway is essential for cyclic and acyclic, conjugated silylmethyl imides. The photolysis of N-(trimethylsilyl)methyl maleimide generates the tricyclic product. Azomethine ylide intermediates are formed in the reaction of N-trimethylsilylmethyl aroyl imides where the excited state C to O silyl migration occurs.