Syntheses of IAA- and IPA-amino acid conjugates

Amino acid derivatives of IAA and IPA are prepared conveniently and efficiently by coupling of readily available 2a-b with diverse free amino acids 3a-g and (3c+3c') to give compounds 4a-j, (4c+4c') and (4h+4h') in 38-70% yields. Similarly, 2a-b afforded IAA and IPA peptide conjugates 6a-b in 32-40% yields. Complete retention of chirality was supported by NMR and HPLC analysis.     

Syntheses of some hexacarboxylic acid derivatives of hexaazatriphenylene

Synthetic methods and product characterizations for the conversions of 1,4,5,8,9,12-hexaazatriphenylene-hexacarboxylic acid to the corresponding triester triacid, triamic acid, triimide, triester triacid chloride, trimethyl triethyl hexaester, trimethyl ester tri(N,N-dimethyrjamide, hexaamide, tri(N,N,-dimethyr)amide triacid, tri(N,N-dimethyl)amide triacid chloride, and trisphthalhydrazide derivatives are described.     

Syntheses and biological evaluation of B-ring-modified analogues of dafachronic acid A

Synthesis and testing of dafachronic acid A ( 1) and its derivatives 2 and 3 have revealed that 1, and not a further oxidation product, is the natural ligand for the DAF-12 receptor of Caenorhabditis elegans.     

Syntheses and thermal properties of some complexes with 2-mercaptonicotinic acid

The biological activity of a kind of hetero-bimetallic Schiff-base complex was studied using Escherichia coli (E. coli) cell as the target. By microcalorimetry, the difference of anti-bacterial activity between the binuclear Schiff-base and the ligand was determined and analyzed. To analyze the inhibition of the bacterial growth internally, the E. coli cells grown in the presence of hetero-bimetallic Schiff-base complex were observed by scanning electron microscopy. The images in high resolution revealed the damage of outer cell membrane caused the inhibitory effect on E. coli. Inductively coupled plasma-mass spectrometry results proved the absorption of the complex by cells, which confirmed the interaction between the Schiff-base and biological macromolecule.     

Syntheses of biodegradable polymer networks based on polycaprolactone and glutamic acid

Biodegradable trifunctional oligomer was synthesized from polycaprolactone and glutamic acid and characterized by Fourier‐transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopies. Injectable and in situ crosslinkable polymer networks were fabricated by the copolymerization of oligomer with triethylene glycol dimethacrylate (TEGDMA) and used to evaluate the initial compressive strengths, viscosities, shrinkages, thermal stabilities, and biodegradabilities in the forms of polymer network neat resin and their composites with β‐tricalcium phosphate. The initial compressive strengths (CS) values of neat resins ranged from 9.54 to 187.6 MPa. Both neat resins and composites had polymerization shrinkage ranging from 0% to 11.7%, which increased with increasing of TEGDMA contents in resin. Moreover, in polymer composite resins, shrinkage values decreased with increasing filler level from 0% to 4.6%, and exothermic evolution values decreased from 33.5°C to 29.7°C as increasing filler level. The composite with the formulation of (polycaprolactone)‐glutamate triacrylate (PCLGTA)/TEGDMA (25/75) and powder/liquid (P/L) ratio of 1.0 exhibited the highest exothermal and lowest shrinkage values. The increase of oligomer in the formulation led to an increase in viscosity.     

Syntheses and reactions of some 4,5-dihaloimidazole-2-carboxylic acid derivatives

The preparation of 5H,10H-diimidazo[1,2-a:1′,2′-d]pyrazine-5,10-dione ( 2a ) and its 2,3,7,8-tetrabromo- and 2,3,7,8-tetrachloro- analogs ( 2b and 2c , respectively) is reported. These dimers, when allowed to react with various anilines, afford imidazole-2-carboxamides ( 3a-c ).     

Syntheses of methylenolactocin and nephrosterinic acid via diastereoselective acylation and chemoselective reduction-lactonization

The syntheses of methylenolactocin, nephrosterinic acid and their derivatives can be achieved by using the efficient diastereoselective acylation of dimethyl itaconate-anthracene adduct followed by tandem chemoselective reduction-lactonization.     

Syntheses and crystal structures of polymeric ionic triorganotin esters of 3,5-pyridinedicarboxylic acid and 5-nitroisophthalic acid

The triethylammonium dicarboxylatotriorganostannates, [(C₂H₅)₃NH][R₃Sn(3,5-pdc)]?·?mH₂O (3,5-pdc?=?3,5-pyridinedicarboxylate) (m?=?1, R?=?Me 1; m?=?0, R?=?Ph 2, PhCH₂ 3, n-Bu 4), [(C₂H₅)₃NH][R₃Sn(5-nip)] (5-nip?=?5-nitroisophthalate) (R?=?Me 5, Ph 6, PhCH₂ 7, n-Bu 8) have been prepared from triethylamine, 3,5-pyridinedicarboxylic acid, 5-nitroisophthalic acid and triorganotin chloride. Complexes 1–8 have been characterized by elemental, IR, ¹H, ¹³C and ¹¹⁹Sn NMR analyses. Complexes 1, 2, 5 and 6 are also determined by single crystal X-ray diffraction. For 1, 2, 5 and 6, each carboxylate moiety is involved in coordination to a tin center via only one O atom showing that the Sn atoms are five-coordinate and exist in trigonal bipyramidal geometries. Moreover, for 2, 5 and 6, the nitrogen atoms of ammonium are hydrogen bonded to the pendant carboxyl oxygen. In 1, adjacent polymeric chains and triethylammonium are linked by hydrogen bonds through the co-crystallized water molecule, thus a 2D network is formed.     

Syntheses,structures and properties of complexes of indole-3-propionic acid

Three complexes [Zn₂(IPA)₂(phen)₄](HIPA)₂(NO₃)₂·H₂O (1), {[Zn(IPA)₂(bipy)]·3H₂O}_n (2), and {[Mn(IPA)₂(bipy)(H₂O)]·2H₂O}_n (3) (HIPA = indole-3-propionic acid, phen = 1,10-phenanthroline, bipy = 4,4′-bipyridine) were synthesized and characterized by physico-chemical and spectroscopic methods. Complex 1 displays a zero-dimensional structure, whilst 2 and 3 show one-dimensional chains, which are linked into supramolecular networks through hydrogen bonding interactions and/or π···π stacking interactions. The luminescence properties of complexes 1 and 2 were investigated.     

Syntheses of (-)-pelletierine and (-)-homopipecolic acid

Enantiomeric syntheses of (-)-homopipecolic acid and (-)-pelletierine have been achieved by chiral resolution of tropanol followed by Baeyer-Villiger oxidation. The methodology provides a practical route for the synthesis of optically pure piperidines.     

Syntheses of homochiral 1,2-ferrocene-functionalized Lewis acids and acid/base pairs

We report a facile approach for the synthesis of homochiral 1,2-disubstituted ferrocene-functionalized Lewis acids and acid/base pairs. The synthesis is based on chiral induction facilitated by the ortho sulfinyl subsitutent in S-Fc{S(O)p-tol}, S-1, to obtain the key intermediate S,S_p-1,2-fc{S(O)p-tol}(BMes₂), S,S_p-2a (p-tol = C₆H₄Me-4, Mes = C₆H₂Me₃-2,4,6). Subsequent substitution of the -S(O)p-tol substituent in S,S_p-2a gives access to a range of enantiomerically pure S_p-1,2-ferrocene-functionalized Lewis acids and acid/base pairs including the first homochiral 1-phosphino-2-borylferrocene. Enantiomeric excesses (e.e.s) of >95% have typically been achieved using this methodology.     

Adducts of tetraphenylstibium nitrate with nitric acid and of tetraphenylstibium acetate with acetic acid: Syntheses and structures

The reactions of tetraphenylstibium nitrate with nitric acid and of tetraphenylstibium acetate with acetic acid yield adducts Ph₄SbONO₂ · HNO₃ (I) and Ph₄SbOC(O)CH₃ · CHH₃COOH (II). According to X-ray diffraction data, the antimony atom in [Ph₄Sb]⁺[O₂N-O···H···O-NO₂]^? has a tetrahedral coordination. The CSbC bond angles and Sb-C bond lengths vary within 108.04(6)°–109.75(4)° and 2.096(1)–2.098(1) Å, respectively. The anion includes the intermolecular hydrogen bond O(1)–H(1)···O(1)″: the O(1)-H(1), H(1)···O(1)″, and O(1)···O(1)″ distances are 0.91(4), 1.56(4), and 2.460(2) Å, respectively; and the OHO angle is 169(5)°. The nitrate groups are usually planar. Complex II also contains the intermolecular hydrogen bond with the following parameters: O(3)-H(3), 0.92 Å; H(3)···O(2), 1.68 Å; and O(3)···O(2) 2.594 Å; the O(2)H(3)O(3) angle is 172.1°. This H-bond noticeable changes the coordination polyhedron of the antimony atom compared to that in tetraphenylstibium acetate.