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Threefold helical assembly via hy-droxy hydrogen bonds: the 2:1 co-crystal of bi-cyclo-[3.3.0]octane-endo-3,endo-7-diol and bi-cyclo-[3.3.0]octane-endo-3,exo-7-diol.

ABSTRACT: Reduction of bi-cyclo-[3.3.0]octane-3,7-dione yields a mixture of the endo-3,endo-7-diol and endo-3, exo-7-diol (C₈H₁₄O₂) isomers (5 and 6). These form (5)₂·(6) co-crystals in the monoclinic P2₁/n space group (with Z = 6, Z' = 1.5) rather than undergoing separation by means of fractional recrystallization or column chromatography. The mol-ecule of 5 occupies a general position, whereas the mol-ecule of 6 is disordered over two orientations across a centre of symmetry with occupancies of 0.463 (2) and 0.037 (2). Individual diol hy-droxy groups associate around a pseudo-threefold screw axis by means of hydrogen bonding. The second hy-droxy group of each diol behaves in a similar manner, generating a three-dimensional hydrogen-bonded network structure. This hydrogen-bond connectivity is identical to that present in three known helical tubuland diol-hydro-quinone co-crystals, and the new crystal structure is even more similar to two homologous aliphatic diol co-crystals.

SUBMITTER: Chan IYH

PROVIDER: S-EPMC8061109 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Crystal structures of two bi-cyclo-[5.1.0]octa-nes: potassium trans-bi-cyclo-[5.1.0]octane-4-carboxyl-ate monohydrate and cis-bi-cyclo-[5.1.0]octan-4-yl 4-bromo-benzene-sulfonate.

Project description:The crystal structures of the trans-fused compound potassium trans-bi-cyclo-[5.1.0]octane-4-carboxyl-ate monohydrate, K+·C9H13O2-·H2O, (I), and of cis-bi-cyclo-[5.1.0]octan-4-yl 4-bromo-benzene-sulfonate, C14H17BrO3S, (II), have been determined. Compound (I) represents the smallest trans-fused cyclo-propane structure known to date, and features the expected shortening of the bridging C-C bond relative to the other cyclo-propane bond lengths, in contrast to the cis-fused system, (II), where all of the cyclo-propane bond lengths are the same. The bicyclic ring system of (I) is disordered across a crystallographic mirror plane. The geometries of the cis-fused and trans-fused ring systems are compared.

| S-EPMC5588580 | biostudies-other

cis-Cyclo-heptane-1,2-diol.

Project description:The title compound, C(7)H(14)O(2), is a vicinal diol derived from cyclo-heptane with cis-orientated hydr-oxy groups. The mol-ecules shows no non-crystallographic symmetry. The O-C-C-O torsion angles of both mol-ecules present in the asymmetric unit [-66.4 (2) and -66.9 (2)°] are similar to those in trans-configured cyclo-hexane derivatives (including pyran-oses) as well as rac-trans-cyclo-heptane-1,2-diol, but smaller than those in trans-configured cyclo-pentane derivatives (including furan-oses). In the crystal structure, O-H⋯O hydrogen bonds furnish the formation of sheets parallel to [110].

| S-EPMC2971971 | biostudies-literature

Endo-exo synergism in cellulose hydrolysis revisited.

Project description:Synergistic cooperation of different enzymes is a prerequisite for efficient degradation of cellulose. The conventional mechanistic interpretation of the synergism between randomly acting endoglucanases (EGs) and chain end-specific processive cellobiohydrolases (CBHs) is that EG-generated new chain ends on cellulose surface serve as starting points for CBHs. Here we studied the hydrolysis of bacterial cellulose (BC) by CBH TrCel7A and EG TrCel5A from Trichoderma reesei under both single-turnover and "steady state" conditions. Unaccountable by conventional interpretation, the presence of EG increased the rate constant of TrCel7A-catalyzed hydrolysis of BC in steady state. At optimal enzyme/substrate ratios, the "steady state" rate of synergistic hydrolysis became limited by the velocity of processive movement of TrCel7A on BC. A processivity value of 66 ± 7 cellobiose units measured for TrCel7A on (14)C-labeled BC was close to the leveling off degree of polymerization of BC, suggesting that TrCel7A cannot pass through the amorphous regions on BC and stalls. We propose a mechanism of endo-exo synergism whereby the degradation of amorphous regions by EG avoids the stalling of TrCel7A and leads to its accelerated recruitment. Hydrolysis of pretreated wheat straw suggested that this mechanism of synergism is operative also in the degradation of lignocellulose. Although both mechanisms of synergism are used in parallel, the contribution of conventional mechanism is significant only at high enzyme/substrate ratios.

| S-EPMC3436550 | biostudies-literature

Benzene-1,3-diol-1,4-diaza-bicyclo-[2.2.2]octane (1/1).

Project description:There are two independent but virtually identical mol-ecules of each component in the asymmetric unit of the title 1:1 adduct, C(6)H(12)N(2)·C(6)H(6)O(2). In the crystal, the constituents are connected into a supra-molecular chain along the b axis by O-H?N hydrogen bonds. Weak C-H?O bonds cross-link the chains.

| S-EPMC3007329 | biostudies-literature

tert-Butyl N-[(11-exo-benzyl-oxy-carbonyl-8-oxopenta-cyclo-[5.4.0.0.0.0]undecane-11-endo-yloxy)carbon-yl-methyl]carbamate.

Project description:The structure of the title compound, C(26)H(29)NO(7), at 173?K has an inter-molecular N-H?O hydrogen bond. This is one of the few examples where a mono-ketone penta-cyclo-undecane (PCU) mol-ecule exibits hydrogen bonding in the solid state. The dihedral angles of the amide and ester groups are normal and unaffected by the cage structure. A longer than normal C-C bond [1.571?(4)?Å] was found within the cage structure.

| S-EPMC2983419 | biostudies-literature

2-exo,5-endo,8,8,10-Penta-chloro-bornane.

Project description:The title compound, C(10)H(13)Cl(5), is a polychlorinated monoterpene and a Toxaphene congener. This compound is also the only penta-chlorinated derivative of camphene formed via ionic chlorination. Previously, the title compound was thought to be 2-exo,5-endo,9,9,10-penta-chloro-bornane, but X-ray structural analysis showed it to have a different structure and rather to be 2-exo,5-endo,8,8,10-penta-chloro-bornane. The title compound shows static disorder and almost half the molecule was divided in two partitions with an occupancy ratio of 0.575 (major) to 0.425 (minor). The repulsive close contacts of Cl atoms could possibly be the cause for this disorder.

| S-EPMC2961057 | biostudies-literature

Potassium (1R,4R,5S,8S)-4,5,8-trihy-droxy-3-oxo-2,6-dioxabicyclo-[3.3.0]octane-4-sulfonate dihydrate.

Project description:The title salt, K(+)·C6H7O9S(-)·2H2O, formed by reaction of dehydro-l-ascorbic acid with potassium hydrogen sulfite in water, crystallizes as colourless plates. The potassium ion is coordinated by eight O atoms arising from hy-droxy or sulfonate groups. The sulfonate group is bonded to the C atom neighbouring that of the lactone carbonyl group. As is commonly observed in crystalline l-ascorbic acid derivatives, the O atom of the primary hy-droxy group is linked to the second C atom from the lactone C atom, forming a hemi-acetal function, thereby creating a bicyclic system of two fused five-membered rings, both of which have envelope conformations with one of the shared C atoms as the flap. Addition of the sulfur nucleophile occurs from the less hindered face. One of the two independent lattice water mol-ecules has hydrogen bonds to sulfonate O atoms of two different anions and is the acceptor of bonds from hy-droxy groups of two further anions; the second lattice water mol-ecule donates to the carbonyl and a hy-droxy O atom in different anions, and accepts from a hy-droxy O atom in a further anion. Thus, through K-O coordination and hydrogen bonds, the potassium cations, sulfonate anions and water mol-ecules are linked in a three-dimensional network.

| S-EPMC3588254 | biostudies-literature

anti-Tricyclo-[4.2.1.1]deca-3,7-diene-9-endo,10-endo-diol.

Project description:The title compound, C(10)H(12)O(2), was synthesized as a candidate for further functionalization. The asymmetric unit comprises two independent mol-ecules, both of which are situated on a center of symmetry. Both mol-ecules are involved in a network of hydrogen bonding, with each alcohol group participating in one hydrogen bond as a donor and in a second hydrogen bond as an acceptor.

| S-EPMC2959889 | biostudies-other

Topology of cyclo-octane energy landscape.

Project description:Understanding energy landscapes is a major challenge in chemistry and biology. Although a wide variety of methods have been invented and applied to this problem, very little is understood about the actual mathematical structures underlying such landscapes. Perhaps the most general assumption is the idea that energy landscapes are low-dimensional manifolds embedded in high-dimensional Euclidean space. While this is a very mild assumption, we have discovered an example of an energy landscape which is nonmanifold, demonstrating previously unknown mathematical complexity. The example occurs in the energy landscape of cyclo-octane, which was found to have the structure of a reducible algebraic variety, composed of the union of a sphere and a Klein bottle, intersecting in two rings.

| S-EPMC3188624 | biostudies-other

Exo-endo trans splicing: a new way to link.

Project description:In addition to canonical cis splicing, which joins exons from a single pre-mRNA, various forms of trans splicing have been described, whereby two separate precursor transcripts are linked with each other. A new study by Hu et al. in Cell Research characterizes a novel and unusual splicing variation, called exo-endo trans splicing.

| S-EPMC3760619 | biostudies-other

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