Copolymeric polythioesters by lipase-catalyzed thioesterification and transthioesterification of alpha,omega-alkanedithiols.
Linear copolymeric polythioesters [PTE; poly(alpha,omega-alkanedioic acid-co-alpha,omega-alkanedithiols)] were formed in good yield (approximately 69%) by thioesterification of 1,12-dodecanedioic acid with 1,6-hexanedithiol and 1,8-octanedithiol, respectively, catalyzed by immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) in vacuo without a solvent. Similarly, transthioesterification (thiolysis) of diethyl 1,12-dodecanedioate with 1,6-hexanedithiol led to the formation of approximately 66% PTE. Poly (1,12-dodecanedioic acid-co-1,6-hexanedithiol) and poly (1,12-dodecanedioic acid-co-1,8-octanedithiol) were extracted from the reaction mixture using methyl-t-butylether, precipitated at -20 degrees C and the precipitates extracted with boiling i-hexane to yield two fractions of PTE. The i-hexane-insoluble fraction of poly (1,12-dodecanedioic acid-co-1,6-hexanedithiol) shows an average molecular mass (Mw) of 1,212 Da, corresponding to a molecular weight range of up to 13,200 Da and a degree of polymerization of up to 38 monomer units. The i-hexane-insoluble fraction of poly (1,12-dodecanedioic acid-co-1,8-octanedithiol) shows a Mw of 2,360 Da, corresponding to a molecular weight range of up to 19,500 Da and a maximum degree of polymerization of up to 52 monomer units. The low-molecular weight (<800 Da) reaction products of thioesterification of 1,12-dodecanedioic acid with 1,6-hexanedithiol, elucidated by gas chromatography-mass spectroscopy, show the following intermediates: (1) 9,20-dioxo-1,8-dithiacycloeicosane; (2) 17,28-dioxo-1,8,9,16-tetrathiacyclooctacosane; (3) 1,12-dodecanedioic acid methyl(O)ester 6'-S-mercaptohexyl thio(S)ester; and (4) oligomeric linear thioester, formed by thioesterification of two molecules of 1,12-dodecanedioic acid with one molecule of 1,6-hexanedithiol.
Weber
N
N
Institute for Lipid Research, Federal Research Center for Nutrition and Food, Piusallee 68-76, 48147, Münster, Germany. niweber@uni-muenster.de
Bergander
K
K
Fehling
E
E
Klein
E
E
Vosmann
K
K
Mukherjee
K D
KD
D000473:Alkanes / Q000737:chemistry / Q000378:metabolism*; D001709:Biotechnology / Q000379:methods; D004800:Enzymes, Immobilized; D004951:Esterification; D004952:Esters / Q000737:chemistry / Q000378:metabolism*; D008049:Lipase / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D020103:Rhizomucor / Q000201:enzymology; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000378:metabolism*
D000473:Alkanes; D004800:Enzymes, Immobilized; D004952:Esters; D011108:Polymers; D013438:Sulfhydryl Compounds; C093666:Lipozyme; D008049:Lipase