THE CHEMISTRY OF PYRROLIC COMPOUNDS .68. 13'-METHYL AND 15'-METHYL ANALOGS OF DEOXOPHYLLOERYTHROETIOPORPHYRIN (DPEP)

A new synthesis of the 13'-methyl (1a) analogue of dpep is described c ommencing with the, methylation of phylloerythroetioporphyrin (1d) wit h subsequent reduction of the derived tertiary alcohol. The availabili ty of this synthetic material has allowed the presence of this petropo rphyrin as its nickel complex to be confirmed in the Julia Creek oil s hales. The presence of an isomer of this petroporphyrin has been noted in the same deposit, and the structure of this novel fossil porphyrin has been confirmed as the 15'-methyl analogue (1b) of dpep by a synth esis commencing from the 15'-oxoporphyrin (1e). In addition, the 15'- and 13'-methyl analogues of dpep have been synthesized by cylization o f appropriately substituted propenyl- and isopropenyl-porphyrins respe ctively. The origin of these two petroporphyrins is discussed.