New C-protective group for peptide synthesis. Application of 2-(1-adamantyl)-propanol-2 esters.

To investigate the possibility of using the 2-(1-adamantyl)-2-propyl (Adp) ester group for carboxyl protection during peptide synthesis, the tetrapeptide Boc-Phe-Arg(NO2)-Phe-Pro-OAdp (IV) was prepared by the carbodiimide method. In this synthesis the Z group was removed by transfer hydrogenation and the Nps group by treatment with 2-thiopyridone. The Adp group was then cleaved with 3% TFA/DCM, yielding Boc-Phe-Arg(NO2)-Phe-Pro-OH. For subsequent kinetics studies the decapeptide Boc-Leu--Z-Orn-Arg(NO2)-Pro- Pro-Gly-Phe-Ser(Bzl)-Pro-Pro-OAdp (VIII) was synthesized by a 9 + 1 scheme. This peptide was also selectively deblocked. Comparing reaction abilities of Z-Pro-OAdp and Z-Pro-OBut, it was demonstrated that the Adp ester is cleaved by 3% TFA/DCM 230 times faster than the Bu(t) ester. For peptides IV and VIII the ratios between the rates of competitive elimination of the Adp and Boc groups by 3% TFA/DCM are 19 and 64, respectively.

[High performance liquid chromatography of peptide bioregulators, their fragments and derivatives. II. Sorption of peptides from aqueous-organic eluents on octadecylsilylsilica gel and unmodified silica gel]. / Vysokoéffektivnaia zhidkostnaia khromatografiia peptidnykh bioreguliatorov, ikh fragmentov i proizvodnykh. II. Sorbtsiia peptidov iz vodno-organicheskikh éliuentov oktadetsilsililsilikagelem i nemodifitsirovannym silikagelem.

Dependence of the peptide retention upon the organic component concentration in eluent has been studied. A parabolic dependence has been found in a wide range of acetonitrile concentrations. The effect observed with ODS- and unmodified silica as stationary phases extends analytical and preparative potentialities of HPLC of peptides.

[High-performance liquid chromatography of peptide bioregulators, their fragments and derivatives. I. Chromatographic pattern of corticotropin fragments of Zorbax ODS sorbent]. / Vysokoéffektivnaia zhidkostnaia khromatografiia peptidnykh bioreguliatorov, ikh fragmentov i proizvodnykh. I.Khromatograficheskoe povedenie fragmentov kortikotropina na sorbente Zorbax ODS.

The influence of acetonitrile concentration in the eluent and of the peptide hydrophobicity on the capacity factors has been studied. The equation is proposed that describes retention as a function of the eluent characteristics and the peptide composition. The hydrophobicity increments for -COOH, -NH2, and greater than CHCONH-fragments in the studied chromatographic system have been determined. The proposed model of peptide retention is useful for a prior evaluation of the eluent composition that is necessary to elute a compound at a given capacity factor. It can be also used for the qualitative interpretation of peptide chromatograms.