Vinyl glycolic acid

Fig. 7 van Krevelen plot for carbohydrate-derived chemicals, colored by carbon number. VGA vinyl glycolic acid, HBL hydroxybut5Tolactone, GVL y-valerolactone, C5 pentoses, C6 = hexoses, LA levulinic acid, Suer. sucrose, Hemi. hemicellulose... 

G 360 - (Retro-)aldol-tisomerization Vinyl glycolic acid 3 102 3H2O 54 85 1.25 [138]... 

As an illustration of the importance of selective dehydration, the reaction of tetrose sugars in alcoholic media with soluble Sn halides has recently been reported [100]. This presents a homogeneous catalytic system, which delivers both Brpnsted (as HCl) and Lewis (as Sn " or Sn" " ) acids. The final products of this conversion were useful a-hydroxy-acids, such as vinyl glycolic acid as discussed in detail in Chap. 3 of this volume (Dusselier et al.). The first step in the reaction path involves a double dehydration leading to the proposed intermediate vinyl glyoxal, as shown being derived from the tetrose in Fig. 12. The mechanism of the dehydration of tetroses is shown in more detail in steps 1 and 2 in Fig. 13 (tentatively catalyzed by a Sn salt). 

Keywords Biomass-to-chemicals Catalysis Cellulose Renewables Lactic acid Vinyl glycolic acid Biodegradable polymers... 

The next two sections of this review chapter will introduce the reader to the world of lactic acid. The acid is both a key platform chemical of the biorefinery concept, from which other interesting molecules may be formed (Sect. 2), and a monomer for commercial bioplastic polylactic acid (PLA) (Sect. 3). In the platform approach, the assessment from Chap. 1 in this volume [23] proves its value, as it is an equally useful tool to seek out the most desired routes for transforming a biomass-derived platform molecule as it is to select the most relevant carbohydrate-based chemicals from a chemist s point of view. In what follows, the desired catalytic cascade from cellulose to lactic acid will be described (Sect. 4) as well as the specific catalytic data reported for different feedstock (Sects. 5 and 6). Section 7 will introduce the reader to recent synthesis routes for other useful AHA compounds such as furyl and vinyl glycolic acid, as well as others shown in Fig. 1. Before concluding this chapter, Sect. 8 will provide a note on the stereochemistry of the chemically produced AHAs. 

Fig. 18 Successful use of vinyl glycolic acid (VGA) as a monomer for PLA based co-polymers (via hydrolysis of MVG). The vinyl containing polymer was active for thiol-ene...

Particulate systems (e.g., collagen, lactic or glycolic acids, polyanhydride or polyethylene vinyl coacetate) have several potential advantages for the therapeutic delivery of DNA (or of drugs), such as DNA encapsulation within the polymer can protect DNA degradation until release injection or implantation of the polymer into the... 

As pointed out by Heller (2), polymer erosion can be controlled by the following three types of mechanisms (1) water-soluble polymers insolubilized by hydrolytically unstable cross-links (2) water-insoluble polymers solubilized by hydrolysis, ionization, or protonation of pendant groups (3) hydrophobic polymers solubilized by backbone cleavage to small water soluble molecules. These mechanisms represent extreme cases the actual erosion may occur by a combination of mechanisms. In addition to poly (lactic acid), poly (glycolic acid), and lactic/glycolic acid copolymers, other commonly used bioerodible/biodegradable polymers include polyorthoesters, polycaprolactone, polyaminoacids, polyanhydrides, and half esters of methyl vinyl ether-maleic anhydride copolymers (3). 

Poly(vinyl alcohol) also reacts with monochloroacetates to yield glycolic acid ethers (160) ... 

Wang, N. Wu, X.S. Li, J.K. A heterogeneously structured composite based on poly(lactic-co-glycolic acid) micro-spheres and poly(vinyl alcohol) hydrogel nanoparticles for long-term protein drug dehvery. Pharm. Res. 1999, 16 (9), 1430-1435. 

Shaded cells indicate compatibility of polymer with solvent or crosslinker PLA poly(lactic acid), PGA poly(glycolic acid) PLGA poly(lactic-co-glycolic acid), PCL poly(e-caprolactone), PEU poly(ester urethane), PEEUU poly(ester ether urethane), PVA poly(vinyl alcohol), PEO poly(ethylene oxide), HA hyaluronic acid, DMF W,W-dimethylformamide, A4 acetic acid, FA formic acid, DCM dichloromethane, HFIP hexafluoroisopropanol, THF tetrahydrofuran, GA glutaraldehyde, NMMO N-methyl-morpholine A -o, idc/water (NMMO/water)... 

N(backbone ester) s L 1C number of ester (-COO-) groups in the backbone of the polymeric repeat unit, which is defined as described in Section 2.D. For example, N one ester) 0 for poly(vinyl acetate) and for poly(methyl methacrylate), 1 for poly(e-caprolactone) and for poly(glycolic acid) (see Figure 2.4), and 2 for polyethylene terephthalate). 

The possibility of vinyl alcohol rearrangement to acetaldehyde was recognized but not stressed. This rearrangement would make possible the oxidation of acetaldehyde to glycollic acid followed by decomposition and further oxidation of the decomposition products to water and carbon dioxide. 

The surface can be modified by a technique, which combines controlled deposition by electrophoresis of charged moieties, with UV graft-ing. Polyelectrolytes, such as methacryUc acid (MA), AA, 2-acryamido glycolic acid (AAG), 2-hydroxyethyl methacrylate (HEMA) and A-vinyl formamide were used for modification. 

S.D. Patil, F. Papadimitrakopoulos, D.J. Burgess, Dexamethasone-loaded polyOactic-co-glycolic) acid microspheres/poly(vinyl alcohol) hydrogel composite coatings for inflammation control. Diabetes Technol. Ther. 6 (6) (2004) 887-897. 

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