Toshimitsu Hagiwara

Physical properties and enzymatic degradability of copolymers of (R)-3-hydroxybutyric acid and (S,S)-lactide

Abstract Copolymers of ( R )-3-hydroxybutyric acid (( R )-3HB) and ( S,S )-lactide (( S,S )-LA) with a wide range of compositions varying from 5 to 92 mol% ( S,S )-LA were synthesized by the ring-opening copolymerization of ( R )-β-butyrolactone with ( S,S )-lactide at various feed ratios in the presence of 1-ethoxy-3-chlorotetrabutyldistannoxane as a catalyst. The structure and physical properties of P[( R )-3HB- co -( S,S )-LA] were characterized by 1 H and 13 C n.m.r. spectroscopy, X-ray diffraction, differential scanning calorimetry, and optical microscopy. The copolyesters were shown to have a random sequence distribution of ( R )-3HB and ( S,S )-LA monomeric units. The glass-transition temperature of P[( R )-3HB- co -( S,S )-LA] increased linearly from 4 to 59°C as the ( S,S )-LA fraction was increased from 0 to 100 mol%. The degree of X-ray crystallinity of solvent-cast copolyester films decreased from 62% to 18% as the ( S,S )-LA composition was increased from 0 to 28 mol%, and the copolyesters showed a P[( R )-3HB] crystal lattice. In contrast, the X-ray crystallinities of copolymers with ( S,S )-LA fractions of 70 to 100 mol% increased from 22% to 46% with the ( S,S )-LA fraction, and those samples showed a P[( S,S )-LA] crystal lattice. The P[( R )3HB- co -( S,S )-LA] samples with 47 to 70 mol% ( S,S )-LA were amorphous polymers. Enzymatic degradations of P[( R )-3HB- co -( S,S )-LA] films were carried out at 37°C in an aqueous solution containing PHB depolymerase purified from Alcaligenes faecalis or proteinase K from Tritirachium album . The rates of enzymatic degradation by PHB depolymerase of copolymer films ranging from 5 to 18 mol% ( S,S )-LA were higher than that of microbial P[( R )-3HB] film. The highest rate of enzymatic hydrolysis by PHB depolymerase was observed at 5 mol% ( S,S )-LA. Little erosion was observed for the copolyester films ranging in ( S,S )-LA fractions from 47 to 100 mol%. In contrast, the weight loss profile of P[( R )-3HB- co -( S,S )-LA] films with a proteinase K showed the opposite trend in the copolymer composition to that of a PHB depolymerase. The highest rate of enzymatic hydrolysis by proteinase K was observed at 92 mol% ( S,S )-LA.

Ring-opening polymerisation of β-butyrolactone catalysed by distannoxane complexes: study of the mechanism

The mechanism of the ring-opening polymerisation of beta-butyrolactones was studied. The ring-opening polymerisation of BL catatlysed by distannoxane complexes is of a living nature. The polymerisation of racemic BL gave a predominantly syndiotactic P(3HB). The temperature effect on syndiospecificity was used to determine the activation energy (deltaE = Esyndiotactic - Eisotactic) for syndiotactic versus isotactic diad placement. The deltaE value was obtained as -1.49 kcal/mol. The steric control leading to the observed syndiospecificity is due predominantly to diastereomeric interactions between the Sn-coordinated P(3HB) chain end. having a specific chain end stereochemistry, and the incoming BL enantiomeric monomers. The catalytic cycle derived from the mechanism of the polymerisation was proposed.

Chemical synthesis of high molecular weight poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Abstract The reaction of optically active β-butyrolactone with γ-butyrolactone in the presence of a distannoxane complex as a catalyst at 100°C yielded a high molecular weight poly)(3-hydroxybutyrate-co4-hydroxybutyrate).

Synthesis and odor of optically active 2-n-hexyl- and 2-n-heptylcyclopentanone and the corresponding δ-lactones

Enantiomeric 2-n-hexyl- and 2-n-heptylcyclopentanones (3) and (4) have been synthesized by asymmetric hydrogenation of 2-n-hexylidene and 2-n-heptylidenecyclopentanones (1) and (2) with Ru2Cl4[p-tolyl-binap]2NEt3 complexes. The differences in odor qualities between enantiomeric pairs of the ketones 3 and 4 have been found to be small, and the same odor threshold values have been observed between the enantiomeric pairs, although the corresponding δ-undeca- and δ-dodecalactones (6) and (7), synthesized by Baeyer–Villiger oxidation of the chiral ketones 3 and 4, showed a fairly large difference in the threshold values between the enantiomeric pairs.

Synthesis and odor of optically active rose oxide

Abstract Stereoselective synthesis of optically active rose oxide ( 1 ) by KHSO4 and Pd–BINAP-catalyzed cyclization of (3R)- and (3S)-3,7-dimethyl-6,7-octadien-1-ol ( 5 ) is described. One-pot synthesis of the (3R)- and (3S)-allenyl alcohol 5 from (3R)- and (3S)-citronellol ( 2 ) (98% ee) is also described. Furthermore, the odor properties of the four diastereomers of 1 are reported.

Synthesis of poly(3-hydroxyalkanoate)s by ring-opening copolymerization of (R)-β-butyrolactone with other four-membered lactones using a distannoxane complex as a catalyst

The reaction of optically active β-butyrolactone with other four-membered lactones in the presence of 1-ethoxy-3-chlorotetrabutyldistannoxane as a catalyst at 100°C gave a series of poly(3-hydroxyalkanoate)s with high molecular weight in good yields.

Synthesis and odor of optically active trans-2,2,6-trimethylcyclohexyl methyl ketones and their related compounds

Abstract The synthesis characterized by cationic olefin cyclizations accomplished using ketone enol esters and odor of novel (1R,6S)- and (1S,6R)-2,2,6-trimethylcyclohexyl methyl ketones ( 5 ) are described. The stereoselective syntheses of (E)-(1R,6S)- and (E)-(1S,6R)-1-(2,2,6-trimethylcyclohexyl)-2-buten-1-one ( 6 ) and (1R,6S)-ethyl 2,2,6-trimethylcyclohexylcarboxylate ( 7 ), useful raw materials for flavor and fragrance, starting from the (1R,6S)- and (1S,6R)-5 are also described.