Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate: a solvomorphism study

Methyl β-lactoside [methyl β-D-galactopyranosyl-(1→4)-β-D-glucopyranoside] monohydrate, C13H24O11·H2O, (I), was obtained via spontaneous transformation of methyl β-lactoside methanol solvate, (II), during air-drying. Cremer–Pople puckering parameters indicate that the β-D-Galp (β-D-galactopyranosyl) and β-D-Glcp (β-D-glucopyranosyl) rings in (I) adopt slightly distorted 4 C 1 chair conformations, with the former distorted towards a boat form (B C1,C4) and the latter towards a twist-boat form (O5 S C2). Puckering parameters for (I) and (II) indicate that the conformation of the βGalp ring is slightly more affected than the βGlcp ring by the solvomorphism. Conformations of the terminal O-glycosidic linkages in (I) and (II) are virtually identical, whereas those of the internal O-glycosidic linkage show torsion-angle changes of 6° in both C—O bonds. The exocyclic hydroxymethyl group in the βGalp residue adopts a gt conformation (C4′ anti to O6′) in both (I) and (II), whereas that in the βGlcp residue adopts a gg (gauche–gauche) conformation (H5 anti to O6) in (II) and a gt (gauche–trans) conformation (C4 anti to O6) in (I). The latter conformational change is critical to the solvomorphism in that it allows water to participate in three hydrogen bonds in (I) as opposed to only two hydrogen bonds in (II), potentially producing a more energetically stable structure for (I) than for (II). Visual inspection of the crystalline lattice of (II) reveals channels in which methanol solvent resides and through which solvent might exchange during solvomorphism. These channels are less apparent in the crystalline lattice of (I).

Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside): evaluating trends in structural parameters

Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside), C9H18O5, (I), crystallizes from a methanol–ethyl acetate solvent mixture at room temperature in a 4 C 1 chair conformation that is slightly distorted towards the C5 S C1 twist-boat form. A comparison of the structural parameters in (I), methyl α-D-glucopyranoside, (II), α-D-glucopyranosyl-(1→4)-D-glucitol (maltitol), (III), and 3-deoxy-α-D-ribo-hexopyranose (3-deoxy-α-D-glucopyranose), (IV), shows that most endocyclic and exocyclic bond lengths, valence bond angles and torsion angles in the aldohexopyranosyl rings are more affected by anomeric configuration, aglycone structure and/or the conformation of exocyclic substituents, such as hydroxymethyl groups, than by monodeoxygenation at C3. The structural effects observed in the crystal structures of (I)–(IV) were confirmed though density functional theory (DFT) calculations in computed structures (I)c–(IV)c. Exocyclic hydroxymethyl groups adopt the gauche–gauche (gg) conformation (H5 anti to O6) in (I) and (III), and the gauche–trans (gt) conformation (C4 anti to O6) in (II) and (IV). The O-glycoside linkage conformations in (I) and (III) resemble those observed in disaccharides containing β-(1→4) linkages.

Contributions of secondary alcohol–ketone O—H...O=C and furan–acetate Csp 2—H...OOC synthons to the supramolecular packings of two bioactive molecules

The crystal structures of rubescin D (1, C26H30O5) and monadelphin A (2, C30H36O11), bioactive molecules of the vilasinin and gedunin classes of limonoids, respectively, are reported for the first time and the synthons affecting their crystal packings are analyzed on the basis of their occurrences in molecules in the Cambridge Structural Database that share the same moieties. Rubescin D, 1, crystallizes in the space group P21 and its molecular structure consists of three six-membered rings A, C and D having, respectively, envelope, twist-boat and half-chair conformations, and three five-membered rings with half-chair (B and E) and planar conformations (F). Many synthons found in the crystal packing of 1 are in agreement with expectations derived from molecules displaying the same moieties. However, the secondary alcohol–ketone O—H...O=C synthon, which has a low occurrence (2.9%), contributes much to the layered packing, while the furan–ketone Csp 2—H...O=C and secondary alcohol–epoxide O—H...OC2 synthons usually found in these compounds (occurrences of 20.6 and 17.6%, respectively) are missing. The packing of 1 is close to that of ceramicine B (3), but is completely different from that of TS3 (4), suggesting that the absence of the epoxide group in 3 would have favoured the furan–secondary alcohol Csp 2—H...OH synthon and that the missing hydroxy group in 4, a strong hydrogen-bond donor, would have favoured the involvement of water molecules in the crystal packing. The molecular structure of monadelphin A, 2, consists of four six-membered fused rings (A, B, C and D) and one five-membered ring (E); they have twist-boat (A and C), chair (B), screw-boat (D) and planar (E) conformations. The molecule crystallizes in the space group P212121 with the contribution of many synthons usually found in compounds having the same moieties. However, the secondary alcohol–acetate O—H...OOC and secondary alcohol–ketone O—H...O=C synthons (occurrences of 16.7% each in these compounds) are missing. The furan–acetate Csp 2—H...OOC synthon not observed in these compounds greatly contributes to the layered packing of 2. The layered packing is very close to those of 7-oxogedunin (5) and 6-dehydro-7-deacetoxy-7-oxogedunin (6), which both crystallize in the space group P21.

Crystal structure and Hirshfeld surface analysis of 2-{[7-acetyl-8-(4-chlorophenyl)-4-cyano-6-hydroxy-1,6-dimethyl-5,6,7,8-tetrahydroisoquinolin-3-yl]sulfanyl}-N-(4-chlorophenyl)acetamide

In the title molecule, C28H25Cl2N3O3S, the heterocyclic portion of the tetrahydroisoquinoline unit is planar while the cyclohexene ring adopts a twist-boat conformation. The two 4-chlorophenyl groups extend away from one side of this unit while the hydroxyl and acetyl groups extend away from the opposite side and form an intramolecular O—H...O hydrogen bond. The crystal packing consists of layers parallel to the bc plane. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions to the crystal packing are from H...H (37.3%), Cl...H/H...Cl (17.6%), O...H/H...O (11.1%), C...H/H...C (10.9%) and N...H/H...N (9.7%) interactions.

rac-(E,trans)-4-Bromo-10,10-dimethyl-9,11-dioxabicyclo[6.3.0]undec-4-ene

In the title compound, a cyclooctene ring in a twist-boat conformation and a dioxolane ring with a distorted envelope conformation are annulated in a trans configuration. Alternating strands of single enantiomers build up the crystal. Within the strands, the molecules are connected by weak C—H...O hydrogen bonds.

Methyl 5-chloro-4-hydroxy-2,2-dioxo-1H-2λ6,1-benzothiazine-3-carboxylate: structure and Hirshfeld surface analysis

The title compound, C10H8ClNO5S, which has potential analgesic activity, crystallizes in space group P21/n. The benzothiazine ring system adopts an intermediate form between sofa and twist-boat conformations. The coplanarity of the ester substituent to the bicyclic fragment is stabilized by an O—H...O intramolecular hydrogen bond. In the crystal, hydrogen bonds of type N—H...O(SO2) link the molecules into zigzag chains extending along the b-axis direction. Neighbouring chains are linked by both O—H...Cl and C—H...Cl interactions. A Hirshfeld surface analysis was used to compare different types of intermolecular interactions, giving contributions of O...H/H...O = 42.0%, C...H/H...C = 17.3%, Cl...H/H...Cl = 14.2%, H...H = 11.1%.

Silver(I) nitrate two-dimensional coordination polymers of two new pyrazinethiophane ligands: 5,7-dihydro-1H,3H-dithieno[3,4-b:3′,4′-e]pyrazine and 3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:6′,7′-e]pyrazine

The two new pyrazineophanes, 5,7-dihydro-1H,3H-dithieno[3,4-b:3′,4′-e]pyrazine, C8H8N2S2, L1, and 3,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b:6′,7′-e]pyrazine, C12H16N2S4, L2, both crystallize with half a molecule in the asymmetric unit; the whole molecules are generated by inversion symmetry. The molecule of L1, which is planar (r.m.s. deviation = 0.008 Å), consists of two sulfur atoms linked by a rigid tetra-2,3,5,6-methylenepyrazine unit, forming planar five-membered rings. The molecule of L2 is step-shaped and consists of two S–CH2–CH2–S chains linked by the central rigid tetra-2,3,5,6-methylenepyrazine unit, forming eight-membered rings that have twist-boat-chair configurations. In the crystals of both compounds, there are no significant intermolecular interactions present. The reaction of L1 with silver nitrate leads to the formation of a two-dimensional coordination polymer, poly[(μ-5,7-dihydro-1H,3H-dithieno[3,4-b;3′,4′-e]pyrazine-κ2 S:S′)(μ-nitrato-κ2 O:O′)silver(I)], [Ag(NO3)(C8H8N2S2)] n , (I), with the nitrato anion bridging two equivalent silver atoms. The central pyrazine ring is situated about an inversion center and the silver atom lies on a twofold rotation axis that bisects the nitrato anion. The silver atom has a fourfold AgO2S2 coordination sphere with a distorted shape. The reaction of L2 with silver nitrate also leads to the formation of a two-dimensional coordination polymer, poly[[μ33,4,8,10,11,13-hexahydro-1H,6H-bis([1,4]dithiocino)[6,7-b;6′,7′-e]pyrazine-κ3 S:S′:S′′](nitrato-κO)silver(I)], [Ag(NO3)(C12H16N2S4)] n , (II), with the nitrate anion coordinating in a monodentate manner to the silver atom. The silver atom has a fourfold AgOS3 coordination sphere with a distorted shape. In the crystals of both complexes, the networks are linked by C—H...O hydrogen bonds, forming supramolecular frameworks. There are additional C—H...S contacts present in the supramolecular framework of II.

1-Isobutyl-8,9-dimethoxy-3-phenyl-5,6-dihidroimidazo[5,1-a]isoquinolin-2-ium chloride

The molecular salt, C23H26N2O2 +·Cl−, was obtained from 1-isobutyl-8,9-dimethoxy-3-phenyl-5,6-dihydroimidazo[5,1-a]isoquinoline, which was synthesized by cyclocondensation of α-benzoylamino-γ-methyl-N-[2-(3,4-dimethoxyphenyl)ethyl]valeramide in the presence of phosphoryl chloride. The tetrahydropyridine ring adopts a twist–boat conformation. In the crystal structure, centrosymmetric dimers are formed by N—H...Cl and C—H...Cl hydrogen bonds.

A concise and efficient concurrent synthesis of 6,11-dihydrodibenzo[b,e]azepines and 5,6,11,12-tetrahydrodibenzo[b,f]azocines and their conversion to 4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylates and N-acetyl-5,6,11,12-tetrahydrodibenzo[b,f]azocines: synthetic sequence, spectroscopic characterization and the structures of two products

Reaction of 2-allyl-N-benzyl-4-fluoroaniline or 2-allyl-N-benzyl-4-chloroaniline with 98% sulfuric acid leads to the concurrent formation of halogeno-substituted 11-ethyl-6,11-dihydrodibenzo[b,e]azepines, (II), and halogeno-substituted 11-methyl-5,6,11,12-tetrahydrodibenzo[b,f]azocines, (III), in each case in (II):(III) molar ratios of ca 2:1. Further reaction of (II) leads to ethyl 13-ethyl-2-halogeno-4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylate, while acetylation of (III) gives the corresponding N-acetyl derivatives. The dibenzo[b,e]azepine and dibenzo[b,f]azocine ring systems are of importance in forming the core of a variety of bioactive compounds. In ethyl 13-ethyl-2-fluoro-4-oxo-8,13-dihydro-4H-benzo[5,6]azepino[3,2,1-ij]quinoline-5-carboxylate, C22H20FNO3, (IVa), the azepine ring adopts a conformation close to the twist-boat form, and the molecules are linked into a three-dimensional framework structure by a combination of C—H...O and C—H...π(arene) hydrogen bonds. The azocine ring in 5-acetyl-2-chloro-11-methyl-5,6,11,12-tetrahydrobenzo[b,f]azocine, C18H18ClNO, (Vb), adopts the boat–boat conformation and the molecules are again linked by C—H...O and C—H...π(arene) hydrogen bonds, but this time form a sheet structure.