If you include enzymic reactions then an 11-bond example is the cyclisation of squalene epoxide to a number of triterpenoids such as hopanol. In the laboratory this type of acid catalysed cyclisation does occur but I doubt if an 11-bond example is known. Gerry Moss _________________________________________________________________________ Dr GP Moss Telephone: +44 171 775 3262 Department of Chemistry Queen Mary & Westfield College Facsimile: +44 181 981 8745 Mile End Road London E1 4NS, United Kingdom E-mail: g.p.moss@qmw.ac.uk World Wide Web server: http://www.chem.qmw.ac.uk/ IUPAC chemical nomenclature data base: http://www.chem.qmw.ac.uk/iupac/ IUBMB biochemical nomenclature data base: http://www.chem.qmw.ac.uk/iubmb/ chemweb: A list for Chemical Applications of the Internet. To post to list: mailto:chemweb@ic.ac.uk Archived as: http://www.lists.ic.ac.uk/hypermail/chemweb/ To (un)subscribe, mailto:majordomo@ic.ac.uk the following message; (un)subscribe chemweb List coordinator, Henry Rzepa (mailto:rzepa@ic.ac.uk)