title: Chemo-enzymatic preparation of copolymeric polythioesters containing branched-chain thioether groups.
abstract: Branched-chain copolymeric polythioesters (PTE) were formed in good yield (approximately 87%) by chemoenzymatic reactions including thiyl radical-induced addition of 1,6-hexanedithiol to the >C=C< double bond of dimethyl 1,18-octadec-9-enedioate and transthioesterification of polyfunctional dimethyl 1,18-octadec-9-enedioate with bifunctional 1,6-hexanedithiol catalyzed by immobilized lipase from Rhizomucor miehei. The reactions were performed in vacuo at 80 degrees C without a solvent. PTE was extracted from the reaction mixture using methyl-t-butylether and precipitated from i-hexane. The polymer structure of the i-hexane-insoluble PTE precipitate was elucidated by GPC/SEC showing an average molecular mass (Mw) of 1,857 Da corresponding to a molecular weight range of up to 24,000 Da and a maximum degree of polymerization of up to 50 monomer units. Chemical derivatization with TMSH demonstrated the formation of up to approximately 58 mol% of a branched-chain thio(S)ether, i.e., dimethyl S-9-(6-mercaptohexylthio)-1,18-octadecanedioate, and small proportions (approximately 8 mol%) of a dimeric disulfide formed therefrom. The chemical structures of various low-molecular weight (<900 Da) reaction products formed by transthioesterification, addition reaction or disulfide formation of the reactants or reaction intermediates, e.g., 1,18-octadec-9-enedioic acid methyl(O)ester 6'-S-mercaptohexyl thio(S)ester, dimethyl S-9-(6-mercaptohexylthio)-1,18-octadecanedioate, were elucidated by GC-MS. Similarly, dimethyl S-9-(6-S-methylthiohexylthio)-1,18-octadecanedioate and dimethyl 11,18,19,26-tetrathia-10,27-di-(7-carboxymethyl-heptyl)hexatriacontane-1,36-dioate were detected in the reaction mixtures after derivatization with trimethylsulfonium hydroxide.
authors.affiliation: Institut für Lipidforschung, Bundesforschungsanstalt für Ernährung und Lebensmittel, Piusallee 68-76, 48147 Münster, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Fehling
authors.forename: E
authors.initials: E
authors.lastname: Klein
authors.forename: N
authors.initials: N
authors.lastname: Weber
authors.forename: C
authors.initials: C
authors.lastname: Demes
authors.forename: K
authors.initials: K
authors.lastname: Vosmann
mesh_terms: D000473:Alkanes / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D004800:Enzymes, Immobilized; D004951:Esterification; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D011091:Polyesters / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D020103:Rhizomucor / Q000201:enzymology*; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism
chemical_list: D000473:Alkanes; D004800:Enzymes, Immobilized; D004952:Esters; D011091:Polyesters; D013438:Sulfhydryl Compounds; C093666:Lipozyme; D008049:Lipase