title: Solid-state photodimerization of steroid enones.
abstract: Androst-4-ene-3,17-dione (1) and 17alpha-methyltestosterone (2) are dimerized in the solid-state by UV radiation. These substances were selected by a search in the CSD among the steroid enones presenting in the crystalline state an intermolecular short contact between a hydrogen alpha to a carbonyl group and the oxygen of an enone system. Dimerization occurs by transfer of the hydrogen to the oxygen and connection between the two involved carbons. Androst-4-ene-3,17-dione (1) affords dimer 3 and trimer 4, both formed by connection of the C-16 of a molecule with the C-3 of a near one. Irradiation of 17alpha-methyltestosterone (2) gives the isomeric trienones 5 and 6. These compounds are reasonably formed by dehydration of unisolated intermediate products 7 and/or 8 obtained by coupling of two molecules through a linkage between the C-2 and the C-3' carbons. The formation mechanisms of the photoproducts are satisfactory explained on the basis of the molecular arrangement of the monomers in the crystal state. Modeling of the dimeric molecules was done using molecular mechanics calculations. A single-crystal X-ray of the dimer of androst-4-ene-3,17-dione confirms the structural interpretation of spectral data. The conformer found in the solid-state agrees well with the results of molecular mechanics calculations.
authors.affiliation: Istituto di Chimica Biomolecolare CNR, Via Campi Flegrei 34, Comprensorio Olivetti, I-80078 Pozzuoli, Napoli, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: DellaGreca
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Iesce
authors.forename: Lucio
authors.initials: L
authors.lastname: Previtera
authors.forename: Fabio
authors.initials: F
authors.lastname: Temussi
authors.forename: Armando
authors.initials: A
authors.lastname: Zarrelli
authors.forename: Carlo Andrea
authors.initials: CA
authors.lastname: Mattia
authors.forename: Raffaella
authors.initials: R
authors.lastname: Puliti
mesh_terms: D000735:Androstenedione / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019281:Dimerization; D007659:Ketones / Q000737:chemistry*; D008777:Methyltestosterone / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010777:Photochemistry / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013256:Steroids / Q000737:chemistry*
chemical_list: D007659:Ketones; D013256:Steroids; D000735:Androstenedione; D008777:Methyltestosterone