Malolactonate

Benvenuti M and Lenz RW. Polymerization and copolymerization of beta-batyrolactone and benzyl-beta-malolactonate by aluminoxane catalyst. J Polym Sci, Part A Polym Chem, 1991, 29, 793. 

Polymers conjugated with 1-adamantyl moieties as lipophilic pendent groups can be utilized to design nanoparticulate dmg delivery systems. Polymer (1) in Fig. 26, which is synthesized by homopolymerization of ethyladamantyl malolactonate, can be employed as highly hydrophobic blocks to construct... 

Poly(malic acid) is a biodegradable and bioadsorbable water-soluble polyester having a carboxylic acid in the side chain. The chemoenzymatic synthesis of poly(malic acid) was achieved by the lipase-catalyzed polymerization of benzyl (3-malolactonate, followed by the debenzylation. The molecular weight of poly(benzyl (3-malolactonate) increased on copolymerizafion with a small amount of (3-PL using lipase CR catalyst. ... 

Chemoenzymatic synthesis of biodegradable poly(malic acid) was performed by lipase-catalyzed polymerization of benzyl /J-malolactone, followed by the debenzylation [72]. The addition of a small amount of /J-PL (17 mol % for the monomer) increased Mw up to 3 x 104 [73]. 

Bizzari R, Chiellini F, Solaro R, Chiellini E, Cammas-Marion S, Guerin P (2002) Synthesis and characterization of new malolactonate polymers and copolymers for biomedical applications. Macromolecules 35 1215-1223... 

Gale et al. (4) prepared the polymeric reaction product of benzyl malolactonate,... 

An interesting derivative of PHB, poly(P-malic acid) (PMA), has been synthesized from -benzyl malolactonate followed by catalytic hydrogenolysis. PMA differs from PHB in that the -(CHa) substituent is replaced by — COOH [Kimura, 1993]. The introduction of pendant carboxylic acid group would make PMA more hydrophilic and easier to be absorbed. 

Racemic Malolactonate. The first cyclic monomer prepared was the benzyl ester of the 3-lactone of malic acid. Initial attempts to make the lactone directly from malic acid itself were unsuccessful, so bromosuccinic acid was chosen as the starting material. This compound was converted to its anhydride by refluxing in acetyl chloride, and the anhydride was reacted with benzyl alcohol to yield a mixture of the two bromosuccinic acid monobenzyl ester isomers. Only one of these esters, IIIB, is capable of being converted to the lactone by... 

Optically Active Benzyl Malolactonate. The route used to prepare the racemic monomer was not applied to the preparation of the optically active monomer because the optically active form of bromosuccinic acid is difficult to prepare and racemization could occur in the S 2 ring-closure reaction. The starting material instead was L-malic acid itself, which is readily available, and the following scheme shows the method of preparation of the optically active malolactone benzyl ester monomer. It should be noted in this scheme that at no time, during the different steps of the synthesis sequence, were bonds made or broken at the chiral carbon atom ... 

The benzyl ester of malolactone was used as the monomer instead of malolactonic acid to eliminate potential problems in the ionic polymerization reactions. The carboxylic acid group, if present, could react with the initiators or cause either chain transfer or termination reactions during the polymerization. The polyester of this pendant ester was readily converted to poly-3-malic acid by hydrogenolysis without change in its molecular weight, according to the following reaction ... 

In the present study, it was important that the L-malolactone benzyl ester monomer be polymerized to the polyester in sufficiently high molecular weights for the biomedical applications in mind. 

Table 1. Polymerization of Racemic Malolactone Benzyl Ester...

DSC analysis of the optically active poly-L-malolactone benzyl ester also showed multiple endotherms in the temperature range of 140-160regardless of the catalyst system used to prepare the polymer. The difference in the melting points of the optically active and racemic polymers could be due to differences in either the degree of stereoregularity or the molecular weights of the polymers. 

The extremely important effect of monomer purity on polymer molecular weight can be seen in Table 3. The impurities in the monomer are, most likely, the cause of the very low molecular weights obtained in Tables 1 and 2. Reactive impurities are apparently still present even after careful purification of the monomer and are assumed to be either malolactone carboxylic acid or benzyl alcohol, formed by hydrolysis of the malolactone benzyl ester during the monomer distillation. The results in Tables 1 and 2 are for experiments made with monomer which has been purified through only one purification by HPLC and distillation. 

Guerin, P., Francillette, J., Brand, C.. and Vert, M. (1986) Benzyl esters of optically active malic acid stereocopohmers as obtained by ring-opening pohanerization of (R)-(+) and (S)-(-)-ben7.yI malolactonates. Makromol. Chem. Macromot. Ssmp., 6, 305-314. 

Four-membered ring lactones 3-propiolactone (P-PL) [68-70], P-butyrolactone (P-BL) [71-76], benzyl P-malolactonate (BBM) [77] and a-methyl-P-propiolactone (MPL) [78, 79] were polymerised using different lipases (Table 12.5). 

The effective polymerization of 0-substltuted-6-lactones seems to be limited to cationic initiators in most reports to date. However, it was recently observed that activation of the 3-position by a carboalkoxy substituent makes anionic polymerization possible, specifically in the case of the esters of malolactone (9), as shown in Equation... 

Chemical conversion Epoxidized triglycer- p-Malolactonate Fatty acids containing unsaturated Furfural a... 

Propen-3-ol and 3-methyl-3-butenol have been used to introduce an unsaturation in P-substituted p-lactones according to the aspartic route (Figure 2). These new malolactonic esters have been polymerized or copolymerized with benzyl malolactonate leading to high molecular weight functional polyesters. 

Cammas-Marion, S., and Guerin, Ph., 2000, Design of malolactonic acid esters with a large spectrum of specified pendant groups in the engineering of biofunctional and hydrolyzable polyesters. Afacromo/. Symp. 153 167. 

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