No abstract

Colouring Matters Derived from Pyrroles. Part I I .

A diuretic peptide Locusta-DP, identified by its ability to increase cyclic AMP production in locust Malpighian tubules in vitro, has been isolated and characterized from whole heads of Locusta migratoria. The purified peptide stimulates fluid secretion by Malpighian tubules maximally in vitro. The primary structure of Locusta-DP was established as a 46 residue amidated peptide: MGMGPSLS IVN PMDVLRQRLLLEIARRRLRDAEEQI KANKDFLQQ I-NH 2 . Locustahas 48% sequence identity with Achetaand 49% identity with Manduca-, and provides further evidence for the presence of a family of diuretic peptides in insects.

An oxidative cyclisation involving the terminal methyl groups of bilenes and biladienes can be brought about by the action of cupric acetate and yields porphyrins. Reaction of bilene-b derivatives with aluminium chloride causes fission at the terminal methylene bridges and also yields porphyrins by combination of two dipyrromethene fragments.

Metallic derivatives of the 5,5"-bi(dipyrromethene) (I ; R = Br) reacted with hydrochloric acid, ammonia, methylamine, and sodium sulphide to yield the corresponding metallic complexes of the macrocyclic systems (VI; X = 0, NH, NMe, and S). Several reactions of the products are described including the formation of the free base (111) and certain macrocyclic ring openings.ALTHOUGH much is known of the chemistry of porphyrins and azaporphyrins, few modifications of the carbon skeletons of these macrocyclic ring systems have been achieved. The elucidation of the structure of vitamin B,, suggested that porphyrins lacking one bridging carbon atom might be capable of existence and we have examined this possibility. In an earlier paper,l the cyclisation of the palladium derivative of the 5,5"-bi(dipyrromethene) * (I; R = Br) with formaldehyde and hydrochloric acid was described and the macrocyclic product was thought to be the palladium derivative (11). Such a reaction had been used to prepare dipyrromethenes from 2-iodopyrroles. However, a re-examination 4 of our product has shown that it is the palladium derivative of the cyclic ether (111).* This nomenclature is now used, in preference t o bi(dipyrromethen-5-y1), so as to be consistent with that of the bipyrroles (cf., inter alia, the preceding paper). The numerals preceding the doubling prefix " bi " denote the points of union of the dipyrromethene units; the series 1-5, 1'--5' of one of these units corresponds to 1'/-5", 1111-5'" of the other.