Die Synthese des ß‐Melanotropins (ß‐MSH) mit der Aminosäurensequenz des bovinen Hormons

The synthesis of an octadecapeptide with the amino‐acid sequence of bovine β‐melanotropin (seryl‐βMSH 10 ) has been accomplished using the same scheme for the protection of amino and carboxyl groups as in the case of α‐melanotropin (αMSH) 9 ), βcorticotropin (ACTH) 1 ) 14 , and active sequences of β‐corticotropin (e.g. β‐ 1–24 ‐corticotropin 13 ) = CIBA 30920‐Ba, Synacthen ®). The compound has been obtained in a very pure state, as shown by thin‐layer chromatography, electro‐phoresis, counter‐current distribution, chromatography on carboxymethyl‐Sephadex ® and amino‐acid analysis. The amino‐acid residues are in the correct (L) configuration, this being ascertained by the methods of synthesis and by enzymic degradation. Synthetic seryl‐βMSH has a distribution coefficient in 2‐butanol/0.5 per cent trichloroacetic acid of 0.56 (1300 transfers) corresponding very closely to that reported for the natural product (same solvents: 0.53; 702 transfers 10 )) [α]   25 D= −57.5° ± 1° (c = 1 in 1 n acetic acid). The product contains 78% peptide, 15.5% water and 6.5% acetic acid (both solvents firmly bound). Its biological activity is 1/10 that of synthetic α‐MSH 9 ).