The 13[2],17[3]-cyclopheophorbide a enol (CPP) is shown to convert mainly to a~1:1 mixture of (13[2]R/S) chlorophyllones a (Chlone), when chromatographed over silica gel or alumina supports. 15[1]-hydroxychlorophyllonelactone a and some other chlorophyll a related compounds are also tentatively identified as minor transformation products of CPP. This raises the possibility that the chlorophyllones reported in recent sediments may be analytical artifacts from CPP. However, data for the surface sediments from Lake Motte as well as literature data for other contemporary sediments show that, (i) they are not artifacts, (ii) considering that CPP is the intermediate compound in the formation of chlorophyllones from chlorophyll a, the hydroxylation of CPP in the sedimentary environment involves an enzymatic process leading preferentially to 13[2]S chlorophyllone a.