The Royal Society of Chemistry Natural Product Reports Editorial Board Professor T J Simpson (Bristol) Chair Dr S L Flitsch (Edinburgh) Dr J R Hanson (Sussex) Dr R B Herbert (Leeds) Professor G Hofle (GBF Germany) Professor J Mann (Reading) Dr D O’Hagan (Durham) Professor D J Robins (Glasgow) Dr C J Schofield (Oxford) Professor J C Vederas (Edmonton Canada) Dr D A Whiting (Nottingham) Editorial Staff Publishing Dr Sheila R Buxton Managing Editor Dr Roxane M Owen Deputy Editor Mrs Dawn J Webb Editoriul Secretary Editorial Office The Royal Society of Chemistry Thomas Graham House Science Park Cambridge UK CB4 4WF International Advisory Board Dr S J Gould (Rahway NJ) Professor H G Floss (Washington OR) Professor L N Mander (Canberra) Professor K Mori (Tokyo) Editorial Staff Production Miss Nicola P Coward Editoriul Production Coordinator Dr Carmel M McNamara Technical Editor Tel+44 (0) 1223 420066 Fax +44 (0) 1223 420247 E-mail perkin@rsc.org RS C Server http //c hemis try.rsc .org/rsc/ Advertisement sales Tel+44 (0) 1223 432240.Fax +44 (0) 1223 426017 Information for Authors Nutural Product Reports is a bimonthly journal of critical reviews. It aims to foster progress in the study of bioorganic chemistry by providing regular and comprehensive reviews of the relevant literature published during well-defined periods. Topics include the isolation structure biosynthesis biological activity and chemistry of the major groups of natural products -alkaloids terpenoids and steroids aliphatic aromatic and 0-heterocyclic compounds.This is augmented by frequent reviews of the wider context of bioorganic chemistry including developments in enzymology nucleic acids genetics chemical ecology primary and secondary metabolism and isolation and analytical techniques which will be of general interest to all workers in the area. Articles in Natural Product Reports are generally commissioned by members of the Editorial Board but the Society is always prepared to consider offers of articles for publication. In such cases a short synopsis rather than the completed article should be submitted to the Managing Editor at the address given above. Natural Product Reports (ISSN 0265-0568) is published bimonthly by The Royal Society of Chemistry Thomas Graham House Science Park Milton Road Cambridge UK CB4 4WF.1998 Annual subscription rate 2380.00. US$685.00. Customers in Canada will be charged the sterling price plus a surcharge to cover GST. Change of address and orders with payment in advance to The Royal Society of Chemistry Turpin Distribution Services Limited Blackhorse Road Letchworth Herts. UK SG6 1HN. Air freight and mailing in the USA by Publications Expediting Service Inc. 200 Meacham Avenue Elmont NY 11003. US Postmaster send address changes to Natural Product Reports Publications Expediting Service Inc. 200 Meacham Avenue Elmont NY 11 003. Periodicals postage paid at Jamaica NY I 143 1-9998. All other despatches outside the UK are by Bulk Airmail within Europe and Accelerated Surface Post outside Europe. The RSC primary and review journals are now available electronically via the Internet. If you take a full price institutional subscription to any RSC primary or review journal you are entitled to free site-wide electronic access to that journal. To access the electronic versions as soon as possible please contact Avril Ross at TDSL Turpin@rsc.org to register your IP addresses. PRINTED in the UK by Henry Ling Ltd at the Dorset Press Dorchester Dorset. 0The Royal Society of Chemistry 1998. All Rights Reserved. No part of this publication may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photographic recording or otherwise without the prior permission of the publishers.