Ozonolysis of (1R,1'R,6R,6'R)-3,3'-methylenebis{6-[(benzyloxy)methoxy]cyclohept-3-en-1 -ol} followed by the diastereo-selective reduction of the resulting beta-hydroxy ketone intermediates gives a rapid route to long-chain polyketides bearing unsymmetrical functions at their terminal positions. These can easily be converted into enantiomerically pure long-chain 1,3-polyol fragments. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).