Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Some plant families have a specialized type of pollination system, with floral lipid rewards for pollinators, which is common. In neotropical Malpighiaceae species like Pterandra pyroidea, this specialized type of pollination system is apparently shifting from floral oils/lipids to pollen reward. Mass spectrometric analysis (GC/MS-EI) indicated that P. pyroidea floral oil has a unique chemical composition, i.e., few fatty acid constituents possessing acetoxy groups at positions 5 and 7, which is distinct from the other floral oils of sympatric Malpighiaceae species. The structure of the major floral oil constituent, a novel fatty acid, anti-5,7-diacetoxydocosanoic acid, was confirmed based on synthesis, mass fragmentation, and H-1 and C-13 NMR analyses; the compound is herein named pterandric acid.101 99102Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PetrobrasUNICAMPConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)