Direct transformation of coumarins into orange-red emitting rhodols

The lactone carbonyl group of coumarin derivatives has been shown to participate in intramolecular Knoevenagel condensations, enabling the unprecedented direct transformation of coumarins into rhodols. The resulting rhodols, possessing two...

6-[(2E)-3,7-Dimethylocta-2,6-dien-1-yl]-5,7-dihydroxy-8-(2-methylbutanoyl)-4-phenyl-2H-chromen-2-one–6-[(2E)-3,7-dimethylocta-2,6-dien-1-yl]-5,7-dihydroxy-8-(3-methylbutanoyl)-4-phenyl-2H-chromen-2-one (1/1) fromMesua elegans

The title co-crystal, C30H34O5·C30H34O5, comprises a 1:1 mixture of two mostly superimposed molecules with the same chemical formula that differ in the nature of the substituent (2-methylbutanoyl or 3-methylbutanoyl) bound at the exocyclic ketone. The lactone ring is close to planar (r.m.s. deviation = 0.058 Å) and the phenyl ring is twisted out of this plane [dihedral angle = 60.08 (9)°]. The geranyl substituent is almost normal to benzene ring to which it is connected [C—C—Car—Car(ar = aromatic) torsion angle = −87.8 (2)°]. Intramolecular O—H...O and O—H...π interactions are formed. In the crystal, supramolecular chains are formed along theaaxis owing to C—H...O contacts, with the lactone carbonyl atom accepting two such bonds.

Crystal chemistry of some synthetic 2-oxa-steroids: conformation, packing motifs and isostructurality

The crystal structures of six synthetic 2-oxa-steroids (A-ring lactone steroids) have been determined by single-crystal X-ray diffraction. The conformation and hydrogen bonding in these oxa-steroids is compared with packing motifs in the natural steroids and the anabolic agent, Anavar®. O—H...O hydrogen bonding with lactone carbonyl O is the preferred arrangement in molecules with a C—OH group. The donor H atoms of A, B and D rings participate in C—H...O interactions with lactone carbonyl O and D-ring hydroxyl/ketone O acceptor atoms. The conformation of the lactone ring in these analogues is different from the natural androgens because replacement of the C2-methylene group by an O atom changes the geometry of the A ring. Two structurally related lactone steroids provide the first example of O—H...O/C—H...O interaction mimicry and furthermore the two components form a binary solid solution. The O—H...O and C—H...O hydrogen bonds in 2-oxa-steroid crystal structures are analysed and the observed preferences discussed in terms of geometric and chemical factors.