José A. Paixão

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A new, straightforward and high yielding procedure to convert oleanolic acid derivatives into the corresponding δ-hydroxy-γ-lactones, by using the convenient oxidizing agent magnesium bis(monoperoxyphthalate) hexahydrate (MMPP) in refluxing acetonitrile, is reported. In addition, a two-step procedure for the preparation of oleanolic 12-oxo-28-carboxylic(More)
A new process using the "ecofriendly" bismuth(III) salts as catalysts for the Westphalen and "backbone" rearrangements of 5 beta,6 beta-epoxysteroids is reported. This method is particularly sensitive to changes on solvent, temperature, stereochemistry of starting epoxysteroid, and its substituent at C17. Depending on the reaction conditions, either(More)
The title steroid, C(23)H(35)ClO(4), is a pregnane derivative prepared by ring opening of the corresponding 5α,6α-ep-oxy steroid with BiCl(3). There are two symmetry-independent mol-ecules in the asymmetric unit that show no significant differences concerning bond lengths and angles. The conformation of the six-membered rings in both mol-ecules is close to(More)
A new convergent synthesis of the antitumor steroid formestane (4-OHA) 5 has been performed from the easily available epimeric mixture of 5 alpha- and 5 beta-androst-3-en-17-one 1a and 1b in order to attempt a yield improvement. A two-step oxidative route followed by base-catalyzed isomerization was applied to the 5 alpha- and 5 beta-epimers 1a and 1b,(More)
The title cholestan, C(28)H(46)O(3), was prepared by epoxidation of 7-norcholest-5-en-3β-yl acetate and crystallized by slow evaporation from an ethano-lic solution. All rings are trans fused. The 3β-acetate and the 17β-cholestane side chain are in equatorial positions. The mol-ecule is highly twisted due to its B-nor characteristic. A quantum chemical(More)
In the title compound, C(17)H(27)NO(4), which is an hydro-sinapic acid derivative with increased lipophilicity conferred by an additional alkyl chain, the central and the hexyl linear chains contain slightly shorter bond lengths [C-N = 1.316 (2) Å; average linear chain C-C = 1.487 (6) Å] than reported average values [Csp(2)-N = 1.334, C-C for CH(2)-CH(2) =(More)
The synthesis and structural elucidation, by 1D and 2D NMR and X-ray diffraction techniques, of novel E/Z 16-azolylmethylene-17-oxoandrostanes 2-9 prepared from the Vilsmeier-Hack reaction product 17-chloro-16-formylandrosta-5,16-dien-3β-yl acetate 1 is reported. The reaction proceeds with pyrrole and pyrrole-alike nitrogen heterocycles such as 7-azaindole,(More)
The title hydrated tetrol, C(19)H(32)O(4)·3H(2)O, was synthesized by stereoselective reduction of the compound 3β,5α,6β-trihy-droxy-androstan-17-one. All rings are fused trans. The organic mol-ecules are connected head-to-tail along the c axis via O-H⋯O hydrogen bonds. Layers of water mol-ecules in the ab plane inter-connect these chains. A quantum chemical(More)
The title compound, C(6)H(6)N(2)O(2)S, is a new polymorphic form of 2-(pyrimidin-2-ylsulfan-yl)acetic acid. Unlike the previous orthorhombic polymorph [Pan & Chen (2009 ▶) Acta Cryst. E65, o652], the mol-ecules are not planar: the aromatic ring makes an angle of 80.67 (17)° with the carboxyl plane. In the crystal, mol-ecules are linked by O-H⋯N hydrogen(More)
DNA is the molecular target for many of the drugs that are used in cancer therapeutics. Of particular interest are the minor groove binders, a group of DNA interactive agents that bind to specific regions of the genome and show significant toxicity towards cancer cells [1]. Alkylating agents induce permanent DNA damage and exhibit potent antitumor activity.(More)