2,3- trans -3,4- trans -3,4-Dihydroxy-L-proline: An amino acid in toxic peptides of Amanita virosa mushrooms

Among the four possible stereoisomers of 3,4-dihydroxy-L-proline,2,3-trans -3,4-trans -3,4-dihydroxy-L-proline (IV) had not been found in nature previously. It has now been detected as a component of virotoxins, toxic peptides ofAmanita virosa mushrooms. Because periodate failed to effect an oxidative glycol splitting reaction, the two hydroxyl groups in positions 3 and 4 were expected to be in atrans configuration. Furthermore, the formation of a 4-lactone on treatment with acids pointed to the carboxyl group and the hydroxyl group at position 4 being in acis configuration. These results are in agreement with structure IV only. Final proof for structure IV was given by NMR spectroscopy and direct comparison with the 2,3-cis -3,4-trans -3,4-dihydroxy-L-proline isomer.