Towards the enantioselective synthesis of (−)-euonyminol - preparation of a fully functionalised lower-rim modelElectronic supplementary information (ESI) available: Crystallographic analysis for compounds 6, 17, 18c, 28a and 31 including CIF files and NMR spectra for all new compounds. CCDC 905361-905365. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3ob27187k

The development of a stereoselective total synthesis of β-dihydroagarofuran 4 is described. This compound contains the same oxygenation pattern on its 'lower-rim' as found in the natural sesquiterpene (−)-euonyminol ( 1 ) and it is expected that the route described should be applicable to the synthesis of that complex natural product. (−)-Euonyminol is found as the core scaffold of a series of complex macrodilactone sesquiterpenoids isolated from the Celastraceae which possess interesting biological activities ( e.g. anti-HIV activity). The synthetic route builds upon an epoxidative asymmetric desymmetrisation of meso -diallylic alcohol 10 that we have reported previously. It features a lactate Ireland-Claisen rearrangement to establish the quaternary stereocentre at C11 ( 27 → 28a ) and an unusual dealkylative intramolecular epoxide-opening by the C11 methyl ether to establish the tetrahydrofuranyl C-ring of the β-dihydroagarofuran skeleton ( 35 → 36 ). A stereoselective synthesis of β-dihydroagarofuran 4 is described. The route features a lactate Ireland-Claisen rearrangement to establish the quaternary stereocentre at C11 and a dealkylative intramolecular epoxide-opening by the C11 methyl ether to close the tetrahydrofuranyl C-ring.