U.S.-Croatia Chemistry Research on Biomimetic Rearrangements in Carbocations

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This U.S.-Croatian research project between Martin Saunders of Yale University and his partner, Olga Kronja of the University of Zagreb, examines the biological pathways important in the formation of steroids and triterpenoids. The researchers seek new fundamental knowledge about the physical organic chemistry of carbocations, including protosteryl cation in animals and dammarenyl cation in plants. These are to be investigated using both experimental techniques and quantum chemical calculations.The US-Croatian team intends to determine the structural features specific for rearrangement of naturally occurring carbocation in biosynthesis. To do so the researchers will investigate the following groups of model carbocations and their parent alcohols or chlorides: 1) the tert-amyl cation, 2) the methylated and deuterated derivatives of 2-cyclopenyl-e-propyl cation and 3) the carbocation derivatives of bicyclo[3.2.0]noname with various alkyl groups at C-1 and C-8. The research plan includes: (a) NMR spectroscopic studies on stable solutions of model carbocations and their isotopically labeled analogues in non-nucleophillic solution, (b) quantum chemical calculations with the model cation and natural cations themselves, and (c) analysis of the rearrangement processes of the model compound in aqueous or nonpolar solvents. Results should yield new insight into details of structure and rearrangements related to chemical behavior of the carbocations involved in biosynthesis of steroids. If successful, this may have implications for future medical research designed to synthesize artificial hormones.This project in organic dynamics of chemistry fulfills the program objective of advancing scientific knowledge by enabling leading experts in the United States and Central Europe to combine complementary talents and pool resources in areas of strong mutual interest and competence.