ORIGIN OF PETROPORPHYRINS .2. EVIDENCE FROM STABLE CARBON ISOTOPES

Compared with the carbon-13 isotopic composition of the ubiquitous C32DPEP (DPEP, deoxophylloerythroetioporphyrin) the heavy but equivalent carbon-13 isotopic composition for the porphyrin structures 15(2)-methyl-15, 17-ethano-17-nor-H-C3oDPEP and 15, 17-butano-, 13, 15-ethano-13(2),17-propano-, and 13(1)-methyl-13, 15-ethano-13(2),17-propanoporphyrin suggests a common precursor, presumably chlorophyll c, for these petroporphyrins isolated from the marine Julia Creek oil shale and the lacustrine Condor oil shale. Similarly, the heavy but variable carbon-13 isotopic composition of 7-nor-H-C31DPEP compared with C32DPEP is consistent with an origin from both chlorophyll 6 and chlorophyll c3. The equivalent carbon-13 isotopic composition for 13(2)-methyl-C33DPEP compared with C32DPEP suggests a common origin resulting from a weighted average of chlorophyll inputs. © 1990, American Chemical Society. All rights reserved.