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The effect of the side chain chiral center position on the secondary structure of oligomers and polymers of N -substituted 4-aminobenzoic acid was studied. Monomer 1 was prepared from l -alanine methyl ester hydrochloride in seven steps. The poly( p -benzamide) having an α-substituted side chain at the nitrogen atom ( α-Me-PA ) was obtained from the polymerization of 1 with triethylsilane, CsF, and 18-crown-6 in THF. The circular dichroism (CD) studies in solution demonstrated that α-Me-PA adopted a right-handed helical conformation in protic polar solvents, such as water and methanol, and a random structure in chloroform, indicating that solvophobic interactions played an important role in the helical folding of α-Me-PA . The tetramer of ( S )-4-( sec -butylamino)benzoic acid was synthesized as a model compound of α-Me-PA . The single crystal X-ray analysis of the tetramer revealed that the right- and left-handed helical molecules existed in a one-to-one ratio in the crystal, and that the screw pitch of the right-handed helix was shorter than the left-handed helix. [ABSTRACT FROM AUTHOR]

Abstract: The historical development of research on the living polymerization process in polycondensation is reviewed. Classical polycondensation is a step-growth process, but a living polymerization polycondensation must proceed by a chain-growth rather than a step growth mechanism. Early work demonstrated that some polycondensations do not obey Flory''s statistical treatment: for example, high molecular weight polymer may be obtained, even at low conversion. This means that a chain-growth mechanism must be involved, with or without a step-growth mechanism. Recent years have seen dramatic development in understanding of polycondensations that proceed only by chain-growth (chain-growth polycondensation). Several possible mechanisms are: (1) activation of the polymer end group by changed substituent effects between the monomer and the polymer, as with aromatic polyamides, polyesters, polyethers, poly(ether sulfone)s and poly(ether ketone)s; (2) activation of the polymer end group by transfer to it of the catalyst, as with polythiophenes; (3) transfer of the reactive species, derived from the initiator, to the polymer end group, as with polymethylenes and polyphosphazenes; and (4) phase-transfer polymerization in a biphase composed of a monomer storage phase and a polymerization phase, as with aliphatic polyesters. These chain-growth polycondensations have been applied to the synthesis of condensation polymers with various architectures: block copolymers, star polymers, graft copolymers, etc. [Copyright &y& Elsevier]

We previously found that expression of the Mm-1 cell-derived transplantability-associated gene 1b (MmTRA1b)/phospholipid scramblase 1 gene was markedly induced during the granulocytic differentiation of human myeloid leukemia cells. To evaluate the role of MmTRA1b expression in human myeloid leukemia, we investigated the relative levels of MmTRA1b transcripts in 81 patients with acute myelogenous leukemia (AML) by the reverse transcriptase polymerase chain reaction. The expression of MmTRA1b in AML-M1, -M5a and -M5b was significantly lower than that in normal bone marrow cells. The levels of MmTRA1b expression in AML-M2 and -M4 varied among patients. Higher MmTRA1b mRNA levels were associated with significantly longer overall survival in AML, especially in AML-M4 patients, independent of chromosomal aberrations such as t(8;21) and inv(16). The present results suggest that the MmTRA1b mRNA level is a new prognostic factor for AML, especially the AML-M4 subtype. [Copyright &y& Elsevier]

• The synthesis of 2-halogenated 4-(isobutylamino)benzoic acids was reported. • Cyclic triamides of the 4-aminobenzoic acids were synthesized by condensation. • Pd-mediated C C bond formation of the cyclic triamide gave a coronene analogue. A coronene analogue containing amide linkage was synthesized from a halogenated cyclic triamide by palladium-mediated intramolecular C C bond formation. The cyclic triamide was formed from the condensation of 2-chloro-4-(isobutylamino)benzoic acid in the presence of dichlorotriphenylphosphorane in 1,1,2,2-tetrachloroethane. By contrast, the condensation of 2-bromo counterpart required silicon tetrachloride in pyridine. The intramolecular C C bond formation, which yielded the target coronene analogue, occurred during the reaction of bromo-substituted cyclic triamide with palladium(II) acetate, triphenylphosphine, and potassium carbonate in N , N -dimethylformamide. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A novel boron-containing compound, benzoxazaborine, was synthesized. • The obtained benzoxazaborines were reasonably stable to hydrolysis. • The oxazaborine ring was the highly planar structure. • The B N bond length indicated an extended π-conjugated system. Abstract Benzoxazaborine derivatives were synthesized by the dehydration condensation reaction of 2-aminobenzyl alcohols with arylboronic acids. The insensitivity of the benzoxazaborines to hydrolysis allowed these compounds to be isolated by silica gel column chromatography. The single crystal X-ray structural analysis demonstrated the highly planar structure of the benzoxazaborine unit, and the B N bond length indicated an extended π-conjugated system. [ABSTRACT FROM AUTHOR]

Abstract: As new and chiral macrocyclophanes with unique structures, variously sized Pn and Mn (n=2–7=number of ‘rod’ segments) with D 2–D 7 symmetry were constructed by alternating connection of axially chiral binaphthyls and linear biphenyls via –CH2O– moieties, so that the macrocycle consists of multiple rod-like naphthalene–biphenyl–naphthalene units linked together at the binaphthyl bonds. The dihedral angle of the two naphthalene rings of binaphthyl is restricted to around 90°, and the calculated values of strain energy difference per naphthalene–biphenyl unit in P2–P7 are almost independent of the macrocycle size, presumably owing to the flexibility of the –CH2O– connectors. [Copyright &y& Elsevier]

Abstract: Vanadium complexes with quinoline ligands (1b–g) and pyridinone ligands (2b–d) were synthesized, and the effect of the length and shape of alkyl chains on the antiproliferative activity toward U937 cells was studied. For the synthesis of the vanadium complexes, quinoline and pyridinone ligands were prepared and then treated with VOSO4 or VO(acac)2. The vanadyl(IV) complexes were characterized by IR, ESR, and UV–vis spectroscopy and elemental analyses. The antiproliferative activity of 1a–g toward U937 cells showed little dependence on the length and shape of the alkyl chain. In contrast, a good correlation was found between the IC50 values and partition coefficients (log P) values of 2a–c. Among them, 2c showed the highest inhibitory activity, and its IC50 value was smaller than that of cisplatin. The apoptosis-inducing ability of 2b and 2c was supported by annexin V-propidium iodide staining experiments and agarose gel electrophoresis analysis. Inhibitors of caspase-3, -8, and -9 did not affect the antiproliferative activity of 2c, indicating that the apoptosis induced by 2c was via a caspase-independent pathway. [Copyright &y& Elsevier]

Abstract: Chain-growth condensation polymerization of 3-(4-octyloxybenzylamino)benzoic acid esters bearing an alkoxy group on the benzene ring was investigated for the synthesis of polyamides having a specific conformation owing to intramolecular hydrogen bonding of CONH⋯OR. The 4-octyloxybenzyl group on the nitrogen of the amide linkage was easily removed with trifluoroacetic acid after polymerization to afford the desired polyamides, which had lower solubility than expected. Furthermore, we found that a cyclic triamide was selectively obtained by slow addition of the base to a solution of the monomer. [Copyright &y& Elsevier]