Grignard reaction on E-ring of methyl pyropheophorbide-α and the synthesis of its deoxy-derivatives

Methyl pyropheophorbide-a and its derivatives substituted by formylmethyl at 3-position were used as starting material for the synthesis of title compounds. The carbonyl groups at 13(1)-position were converted into alkyhydroxy groups by means of Grignard reaction with straight or cyclic alkyl magnesium bromide. The exocyclic carbon-carbon double bond was formed by dehydration reaction to give mono(di)alkylmethylenesubstituted 13(1)-deoxypyropheophorbide derivatives. The stereochemistry of the Grignard reaction on the E-ring was discussed. The structures of all these new compounds were characterized by elemental analysis, UV, IR and H-1 NMR spectra.