In the synthesis of large peptides, the yield and purity of the end-products will be greatly improved when smaller segments are purified prior to their use for fragment coupling either on a solid-phase resin or in solution. The N(alpha)-Fmoc(9-fluorenylmethoxycarbonyl) method allows the selective acidolytic cleavage of fully protected peptides with a free alpha-carboxyl group from the solid-phase resin. For this cleavage, the highly acid-labile HMPB linker, 4-(4-hydroxymethyl-3-methoxyphenoxy)-butyric acid, has been developed. The lipophilic protecting groups, in particular Trt on asparagine, glutamine, and histidine, as well as Pmc (2,2,5,7,8-pentamethylchroman-6-sulfonyl) on arginine, confer a good solubility on most protected peptide segments in organic solution and enable their purification by silicagel chromatography. Whereas the addition of segments on solid-phase resins is often difficult, they can as a rule be coupled easily in solution to give products in high yield and purity. The combined solid-phase and solution strategy is illustrated by the syntheses of human calcitonin-(1-33), human neuropeptide Y, and the sequence 230-249 of mitogen-activated 70K S6 kinase.

Carboxamide functions may be tritylated by an acid-catalyzed reaction with triphenylmethanol and acetic anhydride in glacial acetic acid. The ω-trityl group of asparagine and glutamine is cleavable by TFA, but stable to strong mineral acids in aqueous solution, as well as to nucleophiles and bases. In peptide syntheses, it is ideally suited for combination with side-chain protections of the t.butyl-type.

The trityl (Trt) group is ideally suited for the side-chain protection of His in peptide syntheses, in combination with 9-fluorenylmethyloxycarbonyl (Fmoc) in Nα- and protecting groups cleavable by mild acidolysis in other positions of the peptide. 2,4,5-trichlorophenyl (Tcp)- and pentafluorophenyl (Pfp)-esters of Fmoc-His(Trt)-OH and Trt-His(Trt)-OH are strongly activated, but stable compounds. Nα-Trt is selectively removable in the presence of NIm-Trt.

The synthesis of the new polymeric support of type 7 for the preparation of C-terminal peptide amides by the Fmoc method is described. Cleavage of the peptide amides is performed by very mild acidolysis.

By-product 1 is strongly descreased by 1,2-ethanedithiol, Under too drastic conditions product 2 is formed.

Esterification of Fmoc-amino acids to 4-alkoxybenzyl alcohol polystyrene by 2,6-dichlorobenzoyl chloride represents a convenient method. It is free of the two side-reactions observed with dicyclohexylcarbodiimide/ 4-dimethylaminopyridine, viz. racemization and dipeptide formation.

It is shown that Di-Adoc or Boc as guanidino protecting groups do not prevent the acylation and the subsequent conversion of arginine to ornithine in Fmoc solid phase peptide synthesis.

Somatostatin (SRIF) was applied microiontophoretically to neurons in the frontal and parietal neocortex, the hippocampus and the striatum of rats anaesthetized with either urethane or chloral hydrate. Qualitatively identical results were obtained under both anaesthetic conditions. In urethane-treated rats SRIF elicited a dose-dependent increase of the firing rate of 74% of the neurons studied in the frontal cortex and of 46% of the neurons studied in the parietal cortex. All cortical cells identified as pyramidal cells were excited. In the hippocampus SRIF provoked excitatory responses in two thirds of all neurons. Six out of the nine cells identified as pyramidal cells were excited by SRIF. In the striatum 80% of all neurons were excited. Following repeated exposure of central neurons to SRIF, the magnitude of the excitatory response gradually diminished, indicating desensitisation. SRIF in concentrations ranging from 10(-8) to 10(-4) M did not interfere with the binding of (3H)-muscimol to GABA receptor sites. The release of GABA from synapses preloaded with (3H-GABA) was not influenced by SRIF in the concentration range from 10(-6) to 10(-4) M. These results indicated that SRIF does not evoke the excitatory responses through attenuation of GABA-mediated inhibition. In conclusion, the findings support the hypothesis that somatostatin may function as a neurotransmitter in the central nervous system.