Long-chain polyprenols and rubber in young leaves of Hevea brasiliensis

Long-chain polyprenols consisting of 10-70 cis-isoprene units are present in-the latex of nascent : leaves of young Hevea shoots. A continuous chain-length distribution was observed in these polyprenols, as commonly found in polyprenols isolated from other higher plants. C-13, NMR analysis showed that they contained no omega-dimethylallyl-group at the initiating end, as is the case with,the high and low M-r rubber from Hevea. This finding supports the assumption that the initiating species in the biosynthesis of rubber and polyprenols in Hevea is not tr tms-trans-farnesyl-diphosphate (t,t-FDP) but an FDP, in which the dimethylallyl-group is modified. Alternatively, the initiator is t,t-FDP and the dimethylallyl-group is changed after polymerization. (C) 1998 Elsevier Science Ltd. All rights reserved.