6079-19-2Relevant articles and documents
Oxidation of Δ4- and δ5-steroids with hydrogen peroxide catalyzed by porphyrin complexes of MnIII and FeIII
Rebelo, Susana L. H.,Simoes, Mario M. Q.,M. Graca P. M. S. Neves,Silva, Artur M. S.,Cavaleiro, Jose A. S.,Peixoto, Andreia F.,Pereira, Mariette M.,Silva, Manuela R.,Paixao, Jose A.,Beja, Ana M.
, p. 4778 - 4787 (2007/10/03)
In this paper we describe a new environmentally friendly method to promote the stereoselective epoxidation of Δ4- and Δ5- steroids. Metalloporphyrins efficiently catalyze the epoxidation reactions of 17β-acetoxy-4-androstene (1), 4-cholestene (2) and 3β-acetoxy-5- cholestene (3) in the presence of H2O2 as oxygen donor. Modeling the molecular structure of the porphyrin as well as the central metal allows the control of the preferential formation of α- or β-epoxides. Porphyrins with bulky, electron-withdrawing groups in the ortho positions of the meso phenyls and with MnIII as the central metal ion, such as [Mn(TDCPP)Cl], gave preferentially the β-epoxide of Δ4- and Δ5-steroids. [Fe(TPFPP)Cl] catalyzes preferentially the α-epoxidation of Δ4-steroids and also increases the stereoselectivity for the α-epoxide in Δ5-steroids, similar to the results obtained with m-CPBA (m-chloroperbenzoic acid) as oxidant. The substrate structure strongly influences the chemoselectivity of the reactions. The X-ray structures of two main products were determined, and two-dimensional NMR techniques allowed the full assignment of 1H and 13C NMR resonances as well as the stereochemistry of these products. A mechanistic proposal involving oxo species for the β-approach and peroxy species for the α-approach is proposed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Steroidal N-Nitroamines. Part 3. Pyrolytic Denitroamination of N-Nitroamino-adamantane and -bornane, and of Several Steroidal N-Nitroamines
Francisco, Cosme G.,Freire, Raimundo,Hernandez, Rosendo,Melian, Daniel,Salazar, Jose A.,Suarez, Ernesto
, p. 2325 - 2328 (2007/10/02)
The thermal decomposition of several nitroamines has been investigated.The axial nitroamines 6β-nitroamino-5α-cholestan-3β-yl acetate (1) and 23R-nitroamino-(20S,22S,25S)-5β-spirostan-3β-yl acetate (8) gave exclusively nitrogen-free olefins.The trans-diaxial α-hydroxy nitroamines (2) and (3) afforded the 5α- and 4α-oxirane (6) and (7), and small amounts of the corresponding trans-diols (4) and (5).The 7β- and 7α-nitroaminocholest-5-en-3β-yl acetate (10) and (11) gave 7-oxocholesteryl acetate (14) and a mixture of the 7β- and 7α-alcohol (12) and (13) with 50 and 33percent inversion of configuration, respectively.The oxidation product adamantanone (16) was produced together with adamantan-2-ol (20) in the pyrolysis of 2-nitroaminoadamantane (19).Carbon-carbon rearrangement was observed in the case of exo-2-nitroaminobornane (22) and 20β-nitroaminopregn-5-en-3β-yl acetate (25).The nitroamine (25) yielded the 3-O-acetyl derivatives of pregna-5,20-dien-3β-ol, (29), pregna-5,17(20)(E)-dien-3β-ol, (30), 3β-hydroxypregn-5-en-20-one, (28), 17α-methyl-D-homoandrost-5-ene-3β,17aβ-diol, (31), and a mixture of pregn-5-ene-3β,20-diols (26) and (27).Camphene (23) and tricyclene (24) was obtained from exo-2-nitroaminobornane (22).Mechanisms for the formation of these products are discussed.
