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Copolymers of (R)-3-hydroxybutyric acid ((R)-3HB) and 6-hydroxyhexanoic acid (6HH) with a wide range of compositions varying from 11 to 91 mol % 6HH were synthesized by the ring-opening polymerization of (7?)-/3-butyrolactone with e-caprolactone 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-6HH] were characterized by 1H and 13C NMR spectroscopy, X-ray diffraction, differential scanning calorimetry, and optical microscopy. The copolyesters were shown to have a random sequence distribution of CR)-3HB and 6HH monomeric units. The glass-transition temperature of P[CR)-3HB-co-6HH] decreased linearly from +4 to -67 °C as the 6HH composition was increased from 0 to 100 mol %. The melting temperature of P[(f?)-3HB-co-6HH] samples decreased from 179 to 48 °C as the 6HH fraction was increased from 0 to 43 mol %. Then, the melting temperature of the copolyester increased from 36 to 60 °C with an increase in the 6HH fraction from 81 to 100 mol %. The degree of X-ray crystallinity of solvent-cast copolyester films decreased from 62 to 18% as the 6HH composition was increased from 0 to 43 mol %, and the copolyesters showed a P[(R)-3HB] crystal lattice. On the other hand, the X-ray crystallinities of copolymers with 6HH fractions of 81-100 mol % increased from 31 to 55% with the 6HH fraction, and those samples showed a P(6HH) crystal lattice. The P[(i?)-3HB-co-6HH] samples with 53-70 mol % 6HH were amorphous polymers. Enzymatic degradations of P[(R)-3HB-co-6HH] films were carried out at 25 °C in 0.1 M potassium phosphate buffer (pH 7.4) in the presence of PHB depolymerase purified from Alcaligenes faecalis or of lipase from Rhizopus delemar. The rates of enzymatic degradation by PHB depolymerase of copolymer films ranging from 11 to 43 mol % 6HH were higher than that of bacterial P[(R)-3HB] film. The highest rate of enzymatic hydrolysis by PHB depolymerase was observed at 11 mol % 6HH. Little erosion was observed for the copolyester films ranging in 6HH fractions from 53 to 100 mol %. In contrast, the weight loss profile of P[(R)-3HB-co-6HH] films with a lipase showed a trend in the copolymer composition opposite to that of a PHB depolymerase. The highest rate of enzymatic hydrolysis by lipase was observed at 91 mol % 6HH. HPLC analysis of the water-soluble products liberated during the enzymatic degradation of copolymer films showed a mixture of monomers, dimers, and trimer of (R)-3HB and 6HH units. A model for the enzymatic hydrolysis of the polyester chain by PHB depolymerase was proposed on the basis of the results.

We disclose here that the distannoxane catalysts (2) exhibit a high reactivity in the ring-opening polymerization of /3-butyrolactone to afford poly [(R)-3-hydroxybutyrate] of high molecular weight (A/" > 100 000).

A new hybrid phosphine was designed. The phosphine combines two common structural characteristics found among the effective phosphine ligands reported recently, namely, three tert-alkyl substituents binding to the phosphorus and an aryl group at an appropriate position. A hybrid phospine/palladium system is versatile and effective for the coupling reaction of various aryl halides with primary and secondary amines including carbazole.

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Garlic is used as a spice in cooking due to its unique aroma. The unique aroma of garlic has attracted considerable attention from scientists. The cloves contain large amounts of sulfur-based substances, which as a consequence of their reactive properties, are converted easily to a variety of volatile compounds during processing. The volatile profiles of processed garlic are influenced by processing conditions, such as temperature, pH and solvent. Numerous studies on these changes in volatile compounds that occur during processing have been reported, with a number of types of sulfur-containing volatile compounds being identified in fresh and processed garlic. This review summarizes the volatile components of fresh and processed garlic, particularly those produced by heating and aging. The pungent odor of fresh garlic is contributed mainly to thiosulfinates and their degradation products. During the heating process of garlic, thiosulfinates are mainly decomposed, and nitrogen-containing volatile compounds, such as pyridines and pyrazines are generated. Aldehydes are dominant compounds in black garlic, while esters and phenols are key aroma compounds in aged garlic extract. The slight variations in chemical reactions during the aging process may lead to differences in the aroma of the two types of garlic. Contents 1. Introduction 2. Volatile components of raw garlic cloves 3. Nature of volatile compounds in garlic cloves during heating 4. Comparison of volatile components between black garlic and aged garlic extract 5. Conclusion