Syntheses and conformational analyses of some 3-amino-2,5-dioxo-2,3,4,5-tetrahydro-1H-1-benzazepine derivatives: X-ray crystal structure of 35–3-[[(1,1-dimethylethoxy)carbonyl]amino]-2,5-dioxo-2,3,4,5-tetrahydro-1H-1-benzazepine

The constrained dipeptide mimic 1 was synthesized from 2 in three steps with 65% overall yield. Analyses of the ¹H nmr data of a number of 3-amino-2,5-dioxo-2,3,4,5-tetrahydro-1H-1-benzazepine derivatives led to the conclusion that these compounds adopt a similar conformation and that this ring system is rigid. X-ray crystallography was used to define the structure of 3 , and computer-aided energy minimization of 6 gave a preferred conformation similar to that observed in the crystal of 3 .     

Resolution of triacylglycerol positional isomers by reversed-phase high-performance liquid chromatography

The ability of reversed-phase high-performance liquid chromatography (RP-HPLC) to separate some positionally isomeric disaturated and monounsaturated triacylglycerols (TAGs) as intact species is demonstrated for the first time. Mobile phases of acetonitrile modified with methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, acetone, or dichloromethane were tested for the separation of POP-PPO, PLP-PPL, PEP-PPE, and PDP-PPD (P-palmitic, O-oleic, L-linoleic, E-eicosapentaenoic, D-docosahexaenoic acid residue) on a single RP-HPLC column. The resolution improved with increasing number of double bonds in the acyl residues. While POP and PPO were only partially resolved, PDP and PPD were fully separated with all tested mobile phases, except those containing methanol. Also separated were the four TAGs having the same equivalent carbon number (ECN = 42), PEP, PPE, PDP, and PPD, on a single RP-HPLC column with mobile phase acetonitrile-2-propanol (70:30, v/v) at 0.8 mL/min. In all cases the isomer with the unsaturated acyl residue in either 1- or 3-position was retained more strongly than the respective 2-isomer.     

Regioselective separation of isomeric triacylglycerols by reversed-phase high-performance liquid chromatography: stationary phase and mobile phase effects

Complete regioselective separation of five pairs of isomeric dipalmitoyl polyalkenoyl glycerols with two to six double bonds in the unsaturated acyl residues has been achieved by RP-HPLC on a single ODS column. Four ODS columns with stationary phases containing different percentages of free silanol groups have been tested. Binary mobile phases of ACN admixed with dichloromethane, tetrahydrofuran, 1-propanol, 2-propanol, ethanol, or acetone have been examined. The choice of modifier depended on the nature of the stationary phase. The more polar solvents were better suited for stationary phases with higher percentage of free silanol groups. Isomeric species were eluted according to chain length, number of double bonds, and the position of the unsaturated acyl chain in the glycerol molecule. Retention increases in the order 20:5 < 22:6 < 18:3 < 20:4 < 18:2. Within each isomeric pair, the species with unsaturated acyl chain occupying either the sn-1- or the 3-position were retained preferentially. Complete simultaneous regioselective separation of 10 isomeric triacylglycerols in a single isocratic run on a single ODS column was demonstrated.     

Preparation of 3-substituted 2-dimethylamino-5-(3,5,6-trichloro-1,4-benzoquinon-2-yl)thiazolium salts

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 427–428, March, 1992.     

Novel condensed heterocyclic derivatives of benzofuran based on 2,5-dihydroxy-3,4,6,7tetrachloro-2, 3-dihydrobenzo[b]furan

We have synthesized novel condensed heterocyclic derivatives of benzofuran by reaction of 2,5-dihydroxy3, 4, 6, 7-tetrachloro-2, 3-dihydrobenzo[b]furan (I) with 4-phenyl- and 4-methylthiosemicarbazides, diphenylthiocarbazone, and also via cyclization of 2, 5-dihydroxy-4, 6, 7-trichloro-3-(N, N-diethyldithio-carbarnoyl)-2, 3dihydrobenzo[b]furan (obtained in the reaction of benzofuran I with sodium NN-dithiocarbamate).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 463467, April 1996.     

Synthesis of 3-substituted 5-(3,5,6-trichloro-1,4-benzoquinon-2-yl)thiazoline-2-thiones

By the interaction of 2, 5-dihydroxy-3, 4, 6, 7-tetrachloro-2, 3-dihydrobenzo(bjfuran with salts of N-monosubstituted dithiocarbamic acids, followed by oxidation of the resulting products by benzoquinone, 3-substituted S-(3,5,6-trichloro-1,4-benzoquinon-2-yl)thiazoline-2-thiones have been obtained. An alternative method of synthesis is also proposed, including reaction of the original benzofuran with N-substituted N',N'-dimethylthioureas, cyclization of the resulting thiouronium salt to form 3-substituted 5-(2, S-dihydroxy-3, 4, 6-trichlorophenyl)-2-dimethylattiinothiazolium cations, treatment of these cations with hydrogen sulfide, and subsequent oxidation of the hydroquinone fragment to quinone.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 111–114, January, 1994.