A new stereoselective synthesis of biologically active di- and trienoic acids containing a (1Z,5Z)-diene moiety

Natural (5Z,9Z)-dienoic acids and key precursors of biologically active trienoic acids were prepared in high yields and with high stereoselectivity using cross-cyclomagnesiation of terminal and oxygenated 1,2-dienes with EtMgBr in the presence of Mg metal and Cp₂TiCl₂ catalyst at the key step.