The report contains the recent data about our research on the synthesis and study of the properties of unique natural and synthetic Z,Z-dienoic and Z,Z,Z-trienoic fatty acids exhibiting a wide range of biological activities (antiviral, antibacterial, neuritogenic, antitumor, antiparasitic, fungicidal). All the methods and approaches for the synthesis of the above-mentioned unsaturated carboxylic acids presented in the report are based on the using at the key stage of the synthesis of the catalytic cross-cyclomagnesiation of 1,2-dienes developed by the main co-authors.