Synthesis of regioselectively 18O-labelled chlorophyll derivatives at the 31- and/or 131-positions through one-pot exchange of carbonyl oxygen atoms

Regioselective 18O-labelling of various chlorophyll derivatives were achieved. (R3=CHCH2, COCH3, CH(OH)CH3, CHO and CH2OH; X=H and COOCH3; Y=CH3 and phytyl).