RESUMO
A procedure is described for the preparation of A-homo-5-pregnenes via an acid catalyzed rearrangement of cyclopropylcarbinols assisted by microwave irradiation. 3alpha-Hydroxy and 4alpha-hydroxy-A-homo-5-pregnen-20-one, analogues of the neuroactive steroid allopregnanolone, were obtained by means of a regioselective epoxidation of a double bond in the expanded A-ring, using a fructose-derived chiral ketone as catalyst and oxone as oxidant. Although both these compounds were marginally active in inhibiting TBPS binding to GABA(A) receptors, 3beta-hydroxy-A-homo-5-pregnen-20-one was almost as active as allopregnanolone. Reduction of the double bond of the latter compound resulted in a ten fold loss of activity.
Assuntos
Pregnenos/síntese química , Pregnenos/farmacologia , Receptores de GABA-A/metabolismo , Animais , Compostos Bicíclicos Heterocíclicos com Pontes/metabolismo , Hidróxidos/química , Masculino , Micro-Ondas , Modelos Moleculares , Conformação Molecular , Pregnenos/química , Ligação Proteica/efeitos dos fármacos , Ratos , Ratos WistarRESUMO
Two new sulfated steroidal hexaglycosides, anasterosides A (2) and B (3), along with the known versicoside A (1) have been isolated from the Patagonian starfish Anasterias minuta. Their structures have been elucidated by spectroscopic analysis (NMR and FABMS) and chemical transformations. Compounds 1 and 2 and the synthetic pentaglycoside 1b derived from versicoside A showed antifungal activity against the plant pathogenic fungus Cladosporium cucumerinum. Desulfation of hexaglycoside 1 rendered a totally inactive saponin.