Polyhydroxybutyric acid

The lithium cnolate generated by deprotonation of 2-/m-butyl-6-methyl-l,3-dioxan-4-onc, readily available from polyhydroxybutyric acid (PHB), predominantly affords the diastereo-mers 7 when reacted with aldehydes. The diastereomeric ratios of aldol adducts 7/8, produced by reactions with aliphatic aldehydes, range from 87.5 12.5 to >99 1. Pure diastereoiners7are obtained by recrystallization in 25-74% yield116-118. Only marginal diastereoselectivities with respect to the carbinol center are obtained with aromatic aldehydes111-119. Benzoylation of the dioxanones 7, followed by reduction with lithium aluminum hydride, affords enan-tiomerically and diastereomerically pure triols 9 in >85% yield 11. ... 

The preparation of enantiomerically pure chemicals is also the theme of the next group of four procedures. The biopolymer polyhydroxybutyric acid, which is now produced on an industrial scale, serves as the starting material for the large scale synthesis of (R)-3-HYDROXYBUTANOIC ACID and (R)-METHYL 3-HYDROXYBUTANOATE. Esters of (-)-camphanic acid are useful derivatives for resolving and determining the enantiomeric purity of primary and secondary alcohols. An optimized preparation of (-)-(1S,4R)-CAMPHANOYL CHLORIDE is provided. The preparation of enantiomerically pure a-hydroxyketones from ethyl lactate is illustrated in the synthesis of (3HS)-[(tert)-BUTYL-DIPHENYLSILYL)OXY]-2-BUTANONE. One use of this chiral a-hydroxyketone is provided in the synthesis of (2S,3S)-3-ACETYL-8-... 

Polyhydroxybutyric acid (PHB) is a bacterial biopolymer which has gained much interest because of its potential use as a biodegradable plastic material. This compound is produced by various terrestrial bacteria and serves as an energy reservoir. PHB is usually highly polymeric (10,000 monomer units) and is stored in the bacteria as an insoluble material in inclusion bodies that are visible with an electron microscope 1111]. Although PHB has been inten-... 

Studies on the bulk pyrolysis of polyhydroxybutyric acid from Bacilli and of bacterial polyalkanoates have shown the formation of 2,3-butenoic acid and 2,3-pentenoic acid (18) The presence of 2,3-butenoic acids and pentenoic acid in the pyrolysate of the particulate matter from sample 20C is interpreted as an indication of polyhydroxy-alkanoates in the sample. These mixed polyesters of hydroxy acids with 4, 5 and sometimes 6 carbon atoms are especially abundant in activated sludges (19). The occurrence of m/z 86 and 100 as abundant mass peaks in the spectra of the fluvial material and as very characteristic peaks in the discriminant function spectrum indicates that a significant amount of the mud fraction may consist of sewage debris. This impression was confirmed by identification of a number of other pyrolysis products in the data file. 

No. 16,2003, p.2685-93 PROTEIN ADSORPTION, FIBROBLAST ACTIVITY AND ANTIBACTERIAL PROPERTIES OF POLYHYDROXYBUTYRIC ACID-CO-... 

Polyhydroxybutyric acid is a storage compound for excess carbon in many microorganisms (E 2.2). It may be used in the production of plastics (F 4). Acetoacetic acid, acetone, and /S-hydroxybutyric acid are excreted in the urine of people with a pathologically high blood sugar level (diabetes mellitus) (E 1). Their appearance is of diagnostic value. Butyric acid, butanol, and acetone are products of microbial fermentations. 

Among the naturally occurring PHAs, the best known is the polyhydroxybutyric acid, which is commonly abbreviated as poly(3HB) or PHB. The discovery of poly(3HB) in bacteria is attributed to Maurice Lemoigne of the Pasteur Institute, who in 1925 reported the presence of 3-hydroxybutyric acid in the... 

Macromolecular Chemistry Physics 200, No.2, Feb.l999,p.413-21 THERMAL PROPERTIES AND CRYSTALLISATION BEHAVIOUR OF POLYHYDROXYBUTYRIC ACID IN BLENDS WITH CHITIN AND CHITOSAN Ikejima T Yagi K Inoue Y Tokyo,Institute of Technology... 

Films of blends of polyhydroxybutyric acid with chitin and chitosan were prepared as completely biodegradable... 

G. Biopolymere E biopolym res The term b. is used for all polymers occuring in living organisms, such as - proteins, - polysaccharides, nucleic acids or mostly biotechnologi-cally produced polymers (- microbial gums, - sucrose, biotransformation to biopolymers), that have structures and/or properties similar to natural polymers (- dextrans, - levans, - polyhydroxybutyric acid, - polylactic acid, - pullulan, -+xanthan). 

Another considerable amount is fermented to organic acids, organic solvents, chemical intermediates, yeast and fuel ethanol (- fuel alternatives). Growing interest is focused on its tise as C-source in fermentation for the production of biopolymers , such as - polyhydroxybutyric acid or - polylactic acid. 

Polylactic acid Polyglycolic acid Polycaprolactone Polyhydroxybutyrate Polyhydroxyvalerate... 

Aliphatic polyesters based on monomers other than a-hydroxyalkanoic acids have also been developed and evaluated as drug delivery matrices. These include the polyhydroxybutyrate and polyhydroxy valerate homo- and copolymers developed by Imperial Chemical Industries (ICI) from a fermentation process and the polycaprolactones extensively studied by Pitt and Schindler (14,15). The homopolymers in these series of aliphatic polyesters are hydrophobic and crystalline in structure. Because of these properties, these polyesters normally have long degradation times in vivo of 1-2 years. However, the use of copolymers and in the case of polycaprolactone even polymer blends have led to materials with useful degradation times as a result of changes in the crystallinity and hydrophobicity of these polymers. An even larger family of polymers based upon hydroxyaliphatic acids has recently been prepared by bacteria fermentation processes, and it is anticipated that some of these materials may be evaluated for drug delivery as soon as they become commercially available. 

If the homopolymer decomposes at the fabrication temperature another approach is to make a copolymer that can be melt processed at a lower temperature. For example, polyhydroxybutyrate decomposes at the processing temperature (190°C), whereas the copolymer with valeric acid can be processed at 160°C without decomposition. These aliphatic polyesters are biodegradable and most importantly, the decomposition products are not toxic, hence their use in medical applications (e.g., sutures). 

PE general purpose, ammonia free PE heat resistant, glass fibre reinforced PE impact resistant, cotton filled PE mica filled PerEluoroAlkoxy PolyGlycolic Acid PolyHydroxyAlkanoate PolyHydroxyButyrate... 

Macromolecules may be classified according to different criteria. One criterion is whether the material is natural or synthetic in origin. Cellulose, lignin, starch, silk, wool, chitin, natural rubber, polypeptides (proteins), polyesters (polyhydroxybutyrate), and nucleic acids (DNA, RNA) are examples of naturally occurring polymers while polyethylene, polystyrene, polyurethanes, or polyamides are representatives of their synthetic counterparts. When natural polymers are modified by chemical conversions (cellulose —> cellulose acetate, for example), the products are called modified natural polymers. 

The important bacterial storage material poly-hydroxybutyric acid is related metabolically and structurally to the lipids. This highly reduced polymer is made up of D-(3-hydroxybutyric acid units in ester linkage, about 1500 residues being present per chain. The structure is that of a compact right-handed coil with a twofold screw axis and a pitch of 0.60 nm.a Within bacteria it often occurs in thin lamellae 5.0 nm thick. Since a chain of 1500 residues stretches to 440 nm, there must be 88 folds in a single chain. Present in both cytoplasmic granules and in membranes,b polyhydroxybutyrate can account for as much as 50% of the total carbon of some bacterial In E. coli and many other bacteria polyhydroxybutyrate is present in a lower molecular mass form bound to calcium polyphosphates, proteins, or other macromolecules.d e It has also been extracted from bovine serum albumin and may be ubiquitous in both eukaryotes and prokaryotes.d/e The polymer may function in formation of Ca2+ channels in membranes.b/d... 

Though the interest for synthetic biodegradable polymers is still increasing, few of them are currently available. The best known products are polyhydroxybutyrate, poly(e-caprolactone), poly(glycolic acid), poly(lactic acid) and their copolymer. 

Polyhydroxyalkanoic acids (PHAs) have been extensively researched since the 1970s because of the potential applications of these compounds as biodegradable substitutes for synthetic polymers. The most successful PHA products are the polyhydroxybutyrates (PHBs). The bacterium... 

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