Synthetic studies relevant to biosynthetic research on vitamin B12. Part 6. Synthesis of chlorins by a photochemical approach

Abstract
A rational synthetic route to C-methylated chlorins has been developed in which a seco-chlorin is constructed and then cyclised photochemically by an 18π-electrocyclic process. The conditions of the synthesis are mild and are compatible with the base-sensitive side-chains of the known naturally occurring C-methylated chlorins.