Figure 1. Proposed oxidization of a methyl group at the C7 position of BChlide c to a formyl group in BChl e biosynthesis:

(i) monooxygenation of the 7-methyl to 7-hydroxymethyl group; (ii) monooxygenation of the 7-hydroxymethyl to 7-dihydroxymethyl group followed by the spontaneous dehydration to the 7-formyl group or direct dehydrogenation of the 7-hydroxymethyl to 7-formyl group. The C3¹-stereochemistry is R or S; R¹ =  ethyl, propyl, or isobutyl; R² =  methyl or ethyl.