Synthesis of a novel star-shaped dendrimer by radial-growth polymerization of sarcosine N-carboxyanhydride initiated with poly(trimethyleneimine) dendrimer

A novel AB_n-type dendrimer/linear polymer block copolymer, i.e., poly(trimethyleneimine) dendrimer-block-(polysarcosine)₆₄ ( 1 ), was synthesized by ring-opening polymerization of sarcosine N-carboxyanhydride initiated with the 64-NH₂-terminal poly(trimethyleneimine) dendrimer as a macroinitiator. 1 has narrow molecular weight distributions (M_w/M_n = 1.0₁–1.0₃, by size exclusion chromatography) and controlled polysarcosine chain lengths (by varying the monomer/dendrimer feed molar ratios). Small-angle neutron scattering (SANS) data obtained in D₂O solution of 1 (DP's of polysarcosine = 2.0 and 24) fitted well with a Guinier plot of a spherical particle, and gave diameters of 44 and 100 Å, respectively.     

Globular carbohydrate macromolecule “sugar balls”, 2. Synthesis of mono(glycopeptide)-persubstituted dendrimers by polymer reaction with sugar-substituted α-amino acid N-carboxyanhydrides (glycoNCAs)

Sugar-substituted α-amino acid N-carboxyanhydrides (glycoNCAs), i.e., O-(tetra-O-acetyl-β-D -glucopyranosyl)-L -serine NCA (2a ) and O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D -glucopyranosyl)-L -serine NCA (2b ), were successfully used for the introduction of a mono(glycopeptide) unit into each terminal primary amino group of a dendrimer. Well-defined dendrimer-based artificial glycoconjugates, O-(β-D -glucopyranosyl)-L -serine-persubstituted poly(amido amine) (PAMAM) dendrimer (3a ) and O-(2-acetamido-2-deoxy-β-D -glucopyranosyl)-L -serine-persubstituted PAMAM dendrimer (3b ), were synthesized by polymer reaction of PAMAM dendrimer with 2a and 2b , respectively, followed by deacetylation with hydrazine monohydrate.     

Polypeptide-synthetic polymer hybrids, 1. Miscibility of poly(vinyl alcohol) with poly(sodium α,β-D,L-aspartate)

The present paper describes materials of polypeptide-commodity polymer hybrids from poly(vinyl alcohol) (PVA) and poly(sodium α,β-D ,L -aspartate) ( 1 ). Miscible blend films of polypeptide 1 and PVA were prepared by the solvent-cast method from a homogeneous aqueous solution. Differential scanning calorimetry. Fourier transform infrared, and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (EDX) were used to investigate the blends. It was revealed that 1 and PVA are miscible in a wide range of compositions.     

One-shot block copolymerization

This paper describes a new method of the preparation of block copolymer, in which a mixture of two monomers is subjected to polymerization (simultaneous feeding) by the aid of an initiator. The new method is performed with the polymerization of a family of 2-oxazolines, which proceeds via electrophilic propagating species, cation or covalent bond having electrophilic reactivity. The key to the block copolymer formation with one-shot feeding of monomers is the difference of reactivity of polymerization (nucleophilicity) between the two monomers. First the monomer of higher reactivity is polymerized to completion, and then the monomer of decreased reactivity is polymerized starting from the propagating species of the first polymerization. For the high selectivity of the production of block copolymer, each of two propagations should be of “living mechanism”. Two combinations of monomers, i.e., 2-methyl-2-oxazoline/2-(heptafluoro-n-propyl)-2-oxazoline and 2-phenyl-2-oxazoline/2-(pentafluoroethyl)-2-oxazoline, together with an initiator of methyl tosylate were found to follow the pattern of the new process. Block copolymer of the former monomers' combination was water-soluble, and its aqueous solution showed an excellent value of surface tension.     

Short-step synthesis and structure-activity relationship of cortistatin A analogs

An improved method for synthesizing structurally simplified analogs of cortistatin A (1), a novel anti-angiogenic steroidal alkaloid from a marine sponge, was developed. In contrast to previous methods, step- and redox-economical synthesis was achieved using a known α-bromoketone as the starting material. The structure-activity relationship study revealed that the isoquinoline portion was strictly recognized by the target molecule. Surprisingly, the introduction of the acetamide moiety on the A-ring structure dramatically enhanced the selective antiproliferative activity against endothelial cells. This new method can be easily applied to gram-scale synthesis and enabled us to prepare various analogs, which were focused on the participation of the side chain and A-ring structure.     

Synthesis and degradabilities of polyesters from 1,4:3,6-dianhydrohexitols and aliphatic dicarboxylic acids

Six different polyesters ( 6a–6c and 7a–7c ) were prepared by the bulk polycondensations of the respective combinations of 1,4:3,6-dianhydro-D-glucitol ( 3 ) and 1,4:3,6-dianhydro-D-mannitol ( 4 ) with succinyl dichloride ( 5a ), glutaryl dichloride ( 5b ), and adipoyl dichloride ( 5c ) at 140–180°C. Polyesters having number average molecular weights up to 2.6 ×10⁴ were obtained in high yields. Only polyester 7a based on 4 and 5a was partially crystalline, whereas all the other polyesters were amorphous. Thin films of these polyesters except that of 7a were spontancously hydrolyzed in a neutral phosphate buffer solution at 50°C, whereas they were reluctant to be hydrolyzed at 27°C. The polyesters were more or less degraded at 27°C by treatment with an activated sludge or by prolonged burial in soil. © 1995 John Wiley & Sons, Inc.     

Thick gold-film deposition by high-repetition visible pulsed-laser chemical vapor deposition

A highly conductive gold film, over 10 m-thick with well-controlled linewidth, has been successfully deposited from dimethyl-gold-acetylacetonate and its fluorinated derivative by pyrolytic CVD (Chemical Vapor Deposition) with a high-repetition, visible, pulsed laser. The thermal damage to the polyimide substrate has been substantially suppressed by reducing the thermal diffusion length within 0.2 m in pulsed-laser-induced transient heating, in contrast to the cw laser-CVD scheme. Reproducible and low contact resistance as low as 0.5 between the written line and the existing gold line has been obtained. Sufficiently tough adhesion to polyimide has been observed for the deposit from dimethyl-gold-acetylacetonate. Reasonable agreement has been obtained between the observed deposition characteristics and analytical results for precursor supply rate and temperature increase during short-pulse irradiation.