Structure and biosynthesis mechanism of trans-polyisoprene from chicle

Mori M., . and Nunogaki K., . and Sato Y., . and Tanaka Y., . and Kageyu A., . Structure and biosynthesis mechanism of trans-polyisoprene from chicle. pp. 177-183. ISSN 0127-7065

The structure of both terminal units and arrangement of isoprene units were determined for trans-polyisoprene isolated from chicle resin by crystallisation in hexane. The trans-polyisoprene showed small 13C-NMR signals characteristic of carbons arisen from the dimethylallyl terminal unit and trans-isoprene unit terminated with hydroxyl group. All of the internal isoprene units were estimated to be in the trans configuration. The number average molecular weight estimated from the relative intensity of both terminal units and internal isoprene units was in good agreement with that of 7.9 103 determined by GPC-LALLS measurement. GPC-fractionated samples showed the signals from both terminal units with relative intensities directly proportional to the degree of polymerisation. It was concluded that the trans-polyisoprene from chicle is a high molecular weight homologue of Solanesol consisting of dimethylallyl terminal unit internal trans unit and terminal trans unit substituted for hydroxyl group aligned in that order. The biosynthesis of trans-polyisoprene in chicle was estimated to start from dimethylallyl pyrophosphate by successive addition of isopenetenyl pyrophosphate in trans configuration and to terminate by hydrolysis of the polymer pyrophosphate groups.

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Abstract

The structure of both terminal units and arrangement of isoprene units were determined for trans-polyisoprene isolated from chicle resin by crystallisation in hexane. The trans-polyisoprene showed small 13C-NMR signals characteristic of carbons arisen from the dimethylallyl terminal unit and trans-isoprene unit terminated with hydroxyl group. All of the internal isoprene units were estimated to be in the trans configuration. The number average molecular weight estimated from the relative intensity of both terminal units and internal isoprene units was in good agreement with that of 7.9 103 determined by GPC-LALLS measurement. GPC-fractionated samples showed the signals from both terminal units with relative intensities directly proportional to the degree of polymerisation. It was concluded that the trans-polyisoprene from chicle is a high molecular weight homologue of Solanesol consisting of dimethylallyl terminal unit internal trans unit and terminal trans unit substituted for hydroxyl group aligned in that order. The biosynthesis of trans-polyisoprene in chicle was estimated to start from dimethylallyl pyrophosphate by successive addition of isopenetenyl pyrophosphate in trans configuration and to terminate by hydrolysis of the polymer pyrophosphate groups.

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Item Type:	Article
AGROVOC Term:	Hevea brasiliensis
AGROVOC Term:	Hevea rubber
AGROVOC Term:	Chicle
AGROVOC Term:	Resins
AGROVOC Term:	Biosynthesis
AGROVOC Term:	Isoprene
AGROVOC Term:	Building structures
AGROVOC Term:	Molecular weight
Depositing User:	Ms. Suzila Mohamad Kasim
Last Modified:	24 Apr 2025 06:28
URI:	http://webagris.upm.edu.my/id/eprint/23558

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