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Chloro-formyl steroids as precursors for hybrid heterosteroids: synthesis, spectroscopic characterization, and molecular and supramolecular structures.
Acta Crystallographica. Section C, Structural Chemistry 2018 December 2
Two new functionalized steroids containing both chloro and formyl substituents in ring A, and intended as precursors for the synthesis of hybrid systems, have been synthesized from ketosteroid precursors. 3-Chloro-2-formyl-17,17-dimethyl-18-nor-5α-androstane-2,13-diene, (I), and methyl 3-chloro-4-formyl-12-oxo-5β-cholan-3-ene-24-oate, C26 H37 ClO4 , (IV), have been synthesized using Vilsmeier reactions with 17β-hydroxy-17α-methyl-5α-androstan-3-one and methyl 3,13-dioxo-5β-cholan-24-oate, respectively. These products have been fully characterized using IR spectroscopy, 1 H and 13 C NMR spectroscopy, and high-resolution mass spectrometry, and in the case of (IV), a single-crystal X-ray diffraction study. Crystal structures have also been determined for the known analogues 3-chloro-2-formyl-17-oxo-5α-androst-2-ene, C20 H27 ClO2 , (II), 3-chloro-2-formyl-5α-cholest-2-ene, C28 H45 ClO, (III), and the absolute and relative configurations are assigned for all four compounds (I)-(IV): when the fusion between rings A and B is trans, 3-chloro-2-formyl products are formed, but when this ring fusion is cis, a 3-chloro-4-formyl product results. The formation of (I) involves not only chloroformylation at ring A, but also dehydration and the 1,2 migration of a methyl group at ring D. In each of (II), (III) and (IV), rings B and C adopt almost perfect chair conformations, while ring A adopts a half-chair conformation. Ring D adopts an envelope conformation in each of (II) and (III), albeit differently folded in the two compounds, while in (IV), it adopts a half-chair conformation. A single C-H...O hydrogen bond links the molecules of (II) into C(6) chains which are linked into sheets by means of carbonyl-carbonyl interactions. The molecules of (IV) are linked into simple C(7) chains, again by a single C-H...O hydrogen bond, but there are no direction-specific interactions in (III) that are structurally significant.
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