The preparation of a number of 5,5?-diformyldipyrrylmethanes is described using benzoyl chloride-N,N-dimethylformamide as the formylating mixture.

The haem prosthetic group of lactoperoxidase can be prepared from the enzyme in high yield by reductive cleavage with mercaptoethanol in 8 M-urea under mild conditions. The product yields porphyrins, after removal of iron, which show visible spectroscopic properties similar to protoporphyrin but are considerably more polar. In the presence of iodoacetamide, a different product is obtained by reductive cleavage. The proton n.m.r. and mass spectra of this compound indicate that the prosthetic group of the enzyme is the iron complex of 18-mercaptomethyl-2,7,12-trimethyl-3,8-divinylporphyrin-13,17-d ipropionic acid. It is proposed that the unusual strength of binding of the prosthetic group to the apoprotein is due to formation of a disulphide bond from a cysteine residue to the porphyrin thiol.

Acid-catalyzed ester exchange reactions between diphenyl carbonate and inosine, adenosine, and 5 '-O-tritylinosine have given good yields of the respective nucleoside 2',3'-cyclic carbonates. Prior pro-

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