Use of the silylation reaction in synthesis of fragment 1–4 of the ACTH sequence

A new effective method of synthesizing fragment 1–4 of the ACTH sequence ensuring a high overall yield of the desired product is proposed. This result is achieved thanks to the wide use of the silylation reaction in the synthesis, which has permitted a considerable simplification of the process and the avoidance of the formation of by-products. The peptides synthesized have been characterized by their angles of optical rotation, chromatographic mobilities, and melting points. A table of chemical shifts in the¹³C NMR spectra of the final and intermediate compounds is given.All-Union Research Institute of Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 248–253, March–April, 1988.     

Synthesis of the hexapeptide 11–16 of the natural sequence of human calcitonin

A new variant of the preparative synthesis of hexapeptide 11–16 of the natural sequence of human calcitonin is described. In several of the stages 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline was used successfully as the condensing agent. The final and intermediate compounds were obtained with good yields in chromatographically homogeneous form. Their purity was checked by TLC and measurements of angles of optical rotation. The final product was identified additionally by¹³C NMR. Several physicochemical characteristics of the compounds synthesized (angles of optical rotation, chromatographic mobilities) are given.     

Synthesis of the N-terminal tripeptide sequence of oxytocin with various protective groups for the cysteine residue

The influence of the nature of the protective groups at the sulfur and nitrogen atoms in the cysteine molecule on the reactivity of this amino acid in the peptide condensation reaction has been investigated. The synthesis of the N-terminal tripeptide sequence of oxytocin was selected as a model reaction. For identifying the compounds synthesized and checking their purity, in addition to traditional physicochemical methods (TLC, melting points, angles of optical rotation), wide use has been made of the¹³C NMR method.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 684–692, September–October, 1989.     

Synthesis of fragment 8–12 of the natural sequence of ACTH

Two new variants of the synthesis of the pentapeptide 8–12 of the natural sequence of ACTH are presented. In some stages, the trimethylsilyl group was used as temporary protection of the carboxy group of the amino component. The final and intermediate compounds were obtained with good yields, were distinguished by chromatographic homogeneity, and were characterized by their angles of optical rotation, melting points, and electrophoretic behavior. Their purity was checked by TLC and by high-pressure liquid chromatography. Some physicochemical characteristics (angles of optical rotation, melting points, chromatographic mobilities) of the compounds obtained are given.     

Characteristic and spectroscopic properties of the Schiff-base model compounds

Two series of conjugated aromatic imines (Schiff-base model compounds) with different central groups and various side-group substitutions have been synthesized and characterized by elemental analysis, differential scanning calorimetry (DSC) technique, hydrogen nuclear magnetic resonance (¹H NMR), Fourier transform infrared (FTIR) and ultra-violet and visible light (UV–vis) spectroscopy measurements. The UV–vis absorption of solutions of these compounds in dimethylacetamid (DMA), chloroform and methanol was investigated in the optical range from 240 to 450 nm, where two distinct absorption bands: at 250–280 and 315–360 nm with the different level of absorption have been observed. The influence of compound molecular structure and polarity of solvent on the absorption spectra and the possible optical transitions have been discussed. Structure of diamines in the azomethine models fundamentally affected their spectroscopic properties and conjugation of π-electrons.     

Synthesis and characterization of polyamides obtained from tartaric acid and L-lysine

Two sets of AA · BB-type polyamides (PLyTA) were synthesized from natural compounds L-lysine and D- or L-tartaric acid via the active ester polycondensation method. The carboxyl and hydroxyl side groups were orthogonally protected as methyl ester and methyl ether, respectively. Direct reaction of methyl L-lysinate dihydrochloride with bis(pentachlorophenyl) di-O-methyl tartaric acid led to the aregic polyamide ar-PLyTA, whereas isoregic (ir-PLyTA) and syndioregic (sr-PLyTA) polyamides were obtained by polycondensation of specifically designed amide–aminoacid and amide–diamine monomeric precursors, respectively. These polyamides have intrinsic viscosities in the 0.50–0.76 dl g⁻¹ range, display optical activity, and are readily soluble in chloroform. They start to decompose well above 200 °C and display glass-transition temperatures at 100–105 °C. DSC and X-ray diffraction results indicated that these polyamides are not crystalline but they seem to adopt a partially ordered phase. No differences in properties other than optical rotation were observed between PLyTA made of D- and L-tartaric acid.     

Rational Combination of the Dissolution of Some Inorganic Compounds of Rare-Earth Elements with the Determination of Chemical Forms of Major Constituents in These Compounds

It was found that the major constituents (F^– and S^2–) in fluorides, sulfides, and sulfofluorides of rare-earth elements, and europium(II) in europium fluoride, can be determined titrimetrically. Peculiarities of the decomposition and analysis of initial samples of these compounds and samples after high-temperature treatment in vacuum were considered. The analytical procedures are based on the combination of the decomposition of the test materials using solutions of iodine (determination of S^2–), boric acid (determination of F^–), and vanadium(V) salts (determination of europium(II) salts) and the final titration of excess reagents that selectively reacted with a chemical form of the analyte. Potentiometry with an ion-selective electrode was also used in the determination of fluoride ions. The total concentration of rare-earth elements was determined by chelatometry.     

Synthesis of a modified fragment 13–19 of the sequence of ACTH using silyl protection

A new scheme for the synthesis of a peptide representing a modified analog of fragments 13–19 of the sequence of the adrenocorticotropic hormone has been described, which uses a number of stages the trimethylsilyl grouping for the protection of the carboxy groups of amino acids and peptides. The final and intermediate products were obtained with high yields and were distinguished by chromatographic homogeneity.¹³C NMR was used as a supplementary method for the identification of the compounds. The physicochemical characteristics of the compounds synthesized are given.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormone Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 374–379, May–June, 1980.     

Investigation of some aminophosphonates by high-resolution NMR in the solid

Conclusion By high-resolution NMR in the solid it was possible to demonstrate unambiguously that the nitrogen atom is protonated through the phosphono group in the investigated compounds. The order of substitution of the protons in N-PMG was established from the obtained data on the anisotropy of the³¹P chemical shift in variously substituted salts of N-PMG with CHA. Slow rotation of the phosphono group about the P–C bond was detected during investigation of the hydrochlorides.All-Union Scientific-Research Technological Institute of Herbicides and Plant Growth Regulators. Translated from Zhurnal Strukturnoi Khimii, Vol. 27, No. 3, pp. 60–64, May–June, 1986.