Dioxolane Ring Research Articles

Crystal structures of (±)-(1SR,5SR,6SR,7SR,10SR,11SR,13RS,14SR)-13-hy-droxy-7-meth-oxy-meth-oxy-11,15,18,18-tetra-methyl-3-oxo-2,4-dioxa-tetra-cyclo-[12.3.1.0(1,5).0(6,11)]octa-dec-15-en-10-yl benzoate, its 13-epimer and 13-one derivative.

The title compounds, C29H38O8·0.25C5H12, (A), C29H38O8, (B), and C29H36O8, (C), are tetra-cyclic benzoates possessing a taxane skeleton with a fused dioxolane ring as the core structure. In the asymmetric unit of (A), there are two independent benzoate mol-ecules (A and A') and a half mol-ecule of solvent pentane disordered about an inversion center. The mol-ecular conformations of (A), (B) and (C) are similar except for the flexible meth-oxy-meth-oxy group. The cyclo-hexane, cyclo-hexene and central cyclo-octane rings adopt chair, half-chair and chair-chair (extended crown) forms, respectively. The dioxolane rings are essentially planar, while the dioxolane ring of A' is slightly twisted from the mean plane. In the crystal of (A), inter-molecular O-H⋯O, C-H⋯O and C-H⋯π inter-actions link the independent benzoates alternately, forming a chain structure. In the crystals of (B) and (C), mol-ecules are linked through O-H⋯O and C-H⋯π inter-actions, and C-H⋯O hydrogen bonds, respectively, into similar chains. Further, weak inter-molecular C-H⋯O inter-actions connect the chains into a three-dimensional network in (A) and a sheet in (B), whereas no other interactions are observed for (C).

Synthesis of β-aryl-γ-lactones and relationship: Structure – antifeedant and antifungal activity

Eighteen racemic β-aryl-γ-lactones derived from simple aromatic aldehydes have been obtained in the chemical synthesis. Iodolactones (5c and 6c) were synthesized from (E)-4-(benzo[d][1′,3′]-dioxol-5′-yl)-but-3-en-2-one (1). Reductive dehalogenation of iodolactones 5a–c and 6a–c afforded γ-ethyl-γ-lactones (7a–c, 8a–c) whereas the unsaturated lactones (9a–c, 10a–c) were obtained by dehydrohalogenation of iodolactones. All synthesized lactones were fully characterized by spectroscopic data (NMR, IR, HRMS) and subjected to the tests on the antifeedant activity towards Tribolium confusum, Trogoderma granarium and Sitophilus granaries as well to the tests on the antifungal activity towards four Fusarium species. The biological tests allowed to find some relationships between the structure and biological activity of the compounds studied. γ-Ethyl- γ-lactones 7a–c, 8a–c and unsaturated lactones 9a–c, 10a-c were usually stronger antifeedants than their parent iodolactones 5a–c and 6a–c. trans-Iodolactones 6a–c were more active than cis isomers 5a-c both in antifeedant and antifungal assays. The structure of aromatic substituent was the key factor in antifungal activity. The lactones with benzo [d][1,3]dioxole ring (5c, 6c, 7c, 8c, 9c) were the most active whereas those with unsubstituted benzene ring exhibited almost no activity. Eighteen racemic β-aryl-γ-lactones have been synthesized and subjected to the tests on the antifeedant towards storage pests and antifungal activity towards some Fusarium species. γ-Ethyl-γ-lactones and unsaturated lactones were usually stronger antifeedants than their parent iodolactones. The lactones with benzo [d][1,3]dioxole ring exhibited the highest activity.

Gastroprotective efficacy and safety evaluation of scoparone derivatives on experimentally induced gastric lesions in rodents.

This study investigated the gastroprotective efficacy of synthesized scoparone derivatives on experimentally induced gastritis and their toxicological safety. Six scoparone derivatives were synthesized and screened for gastroprotective activities against HCl/ethanol- and indomethacin-induced gastric ulcers in rats. Among these compounds, 5,6,7-trimethoxycoumarin and 6,7,8-trimethoxycoumarin were found to have gastroprotective activity greater than the standard drug rebamipide; 6-methoxy-7,8-methylenedioxycoumarin, 6-methoxy-7,8-(1-methoxy)-methylenedioxycoumarin, 6,7-methylenedioxycoumarin, and 6,7-(1-methoxy)-methylenedioxycoumarin were found to be equipotent or less potent that of rebamipide. Pharmacological studies suggest that the presence of a methoxy group at position C-5 or C-8 of the scoparone’s phenyl ring significantly improves gastroprotective activity, whereas the presence of a dioxolane ring at C-6, C-7, or C-8 was found to have decreased activity. In order to assess toxicological safety, two of the potent gastroprotective scoparone derivatives—5,6,7-trimethoxycoumarin and 6,7,8-trimethoxycoumarin—were examined for their acute toxicity in mice as well as their effect on cytochrome P450 (CYP) enzyme activity. These two compounds showed low acute oral toxicity in adult male and female mice, and caused minimal changes to CYP3A4 and CYP2C9 enzyme activity. These results indicate that compared to other scoparone derivatives, 5,6,7-trimethoxycoumarin and 6,7,8-trimethoxycoumarin can improve gastroprotective effects, and they have low toxicity and minimal effects on drug-metabolizing enzymes.

ChemInform Abstract: Synthesis, Properties and Transformations of Fullerene Peroxides

AbstractReview: 143 refs.

Crystal structure of (±)-(4RS,5RS,7SR)-4-[(1RS,2RS,3RS,6RS)-3-benzoyloxy-2-(2-hydroxyethyl)-6-methoxymethoxy-2-methylcyclohexyl]-8,10,10-trimethyl-2-oxo-1,3-dioxaspiro[4.5]dec-8-en-7-yl benzoate benzene monosolvate

In the title compound, C36H44O10·C6H6, the dioxolane ring adopts an envelope conformation with the C atom bonded to the H atom as the flap, while the cyclo-hexene and cyclo-hexane rings are in half-chair and chair conformations, respectively. In the crystal, a pair of O-H⋯O hydrogen bonds with an R 2 (2)(26) graph-set motif connect the benzoate mol-ecules into an inversion dimer. The dimers are linked by a weak C-H⋯O inter-action into a tape structure along [01-1]. The benzene mol-ecule links the tapes through C-H⋯O and C-H⋯π inter-actions, forming a sheet parallel to (100).

Crystal structure of (E)-2-[1-(benzo[d][1,3]dioxol-5-yl)ethyl-idene]-N-methyl-hydrazine-1-carbo-thio-amide.

In the title compound, C11H13N3O2S, there is a short intra­molecular N—H⋯N contact. The benzo[d][1,3]dioxole ring system is approximately planar (r.m.s. deviation = 0.025 Å) and makes a dihedral angle of 56.83 (6)° with the mean plane of the methyl­thio­semicarbazone fragment [–N—N—C(=S)—N—C; maximum deviation = 0.1111 (14) Å for the imino N atom]. In the crystal, mol­ecules are linked via pairs of N—H⋯S hydrogen bonds, forming inversion dimers. The dimers are connected by N—H⋯S hydrogen bonds into layers parallel to (100). The H atoms of both methyl groups are disordered over two sets of sites and were refined with occupancy ratios of 0.5:0.5 and 0.75:0.25.

New Modifiers for Bisphenol a Epoxy Resins, Containing a Polychloro-Substituted Norbornene Skeleton

By the interaction of 3-chloro(chloroalkoxy)-1,2-propanediols with 3-cyclohexene-1-carbaldehyde, unsaturated 2,4-disubstituted 1,3-dioxolanes were synthesised, and by their condensation with hexachlorocyclopentadiene, adducts were obtained that combined in their molecules a dioxolane ring with a hexachloro-substituted norbornene skeleton. A study was made of the effectiveness of the latter as plasticiser/ modifiers for epoxy composites based on bisphenol A epoxy resin ED-20.

The conformational behavior, geometry and energy parameters of Menshutkin-like reaction of O-isopropylidene-protected glycofuranoid mesylates in view of DFT calculations

The formation of pyridinium salts in the transformation of three O-isopropylidene-protected mesylates of furanoid sugar derivatives under pyridine action is considered at the B3LYP/6-31+G** computation level. All the structures were optimized in the gas phase, in chloroform and water. Activation barrier heights in the gas phase were also estimated at the B3LYP/6-311++G**, MPW1K/6-31+G** and MPW1K/6-311++G** levels. The conducted calculations, both in the gas phase (regardless of the computation level) and in solvents, revealed the barrier height increasing order as follows: 1>2>3 for the three reactions studied. The conformational behavior of the five-membered ring is discussed in the gas phase and in solvents. The fused dioxolane ring makes the furanoid ring less likely to undergo conformational changes. In the case of reaction 3, the furanoid ring shape does not change either in the gas phase or in solvents. All conformers are close to E0 or 0E.

7,7-[Ethane-1,2-diylbis(oxy)]-2-[hydroxy(phenyl)methyl]bicyclo[3.3.1]nonan-3-one

In the title compound, C18H22O4, the cyclo­hexane and cyclo­hexa­none rings adopt normal chair and half-chair conformations, respectively. The dioxolane ring is almost planar, with an r.m.s. deviation of 0.094 (3) Å. In the crystal, mol­ecules are connected by O—H⋯O hydrogen bonds, forming 21 helical chains along the a-axis direction. The chains are further connected by C—H⋯O hydrogen bonds.

{(3aR,5S,6R,6aR)-5-[(R)-1,2-Di-hydroxy-eth-yl]-2,2-di-methyl-tetra-hydro-furo[2,3-d][1,3]dioxol-6-yl}methyl methane-sulfonate.

In the title compound, C11H20O8S, the furan­ose ring has a pseudorotation phase angle equal to 31.3° and assumes a 3 T 4 conformation, with deviations of 0.297 (4) and −0.152 (4) Å for the corresponding C atoms. The dioxolane ring adopts an envelope conformation. One of the O atoms is at the flap and deviates from the least-squares plane formed by the other four ring atoms by 0.405 (2) Å. The dihedral angle between the planar fragments of the rings is 63.53 (8)°. In the crystal, mol­ecules are associated into sheets perpendiculer to the b axis by means of O—H⋯O hydrogen bonds. A few weak C—H⋯O inter­actions are also observed.

1-Piperonylpiperazinium 4-chloro-benzoate.

In the title salt {systematic name: 1-[(1,3-benzodioxol-5-yl)meth­yl]piperazin-1-ium 4-chloro­benzoate}, C12H17N2O2 +·C7H4ClO2 −, the piperazine ring adopts a slightly disordered chair conformation. The dioxole ring is in a flattened envelope conformation with the methyl­ene C atom forming the flap. The relative orientation of the piperonyl ring system and the piperazine rings is reflected in the N—C—C C torsion angle of 132.3 (1)°. In the anion, the mean plane of the carboxyl­ate group is twisted from that of the benzene ring by 14.8 (9)°. In the crystal, the components are linked by N—H⋯O and weak C—H⋯O hydrogen bonds, forming chains along [010].

6a-Nitro-6-(2,2,7,7-tetramethyltetrahydro-3aH-bis[1,3]dioxolo[4,5-b:4′,5′-d]pyran-5-yl)-6a,6b,7,8,9,11a-hexahydro-6H-spiro[chromeno[3,4-a]pyrrolizine-11,11′-indeno[1,2-b]quinoxaline

In the title compound, C39H38N4O8, the quinoxaline and indene subunits are essentially planar, with maximum deviations of 0.071 (2) and 0.009 (2) Å, respectively. The indeno­quinoxaline system forms a dihedral angle of 72.81 (3)° with the chromenopyrrolizine system. The two dioxolane rings, as well as the pyran ring of the chromeno group and the terminal pyrrolizine, each adopt an envelope conformation with O and C as flap atoms. The central pyrrolizine ring adopts a twisted conformation. Intra­molecular C—H⋯O and C—H⋯N hydrogen bonds occur. The crystal structure exhibits C—H⋯O hydrogen bonds, and is further stablized by C—H⋯π inter­actions, forming a two-dimensional network along the bc plane.

Bis{4-[(1,3-benzodioxol-5-yl)meth-yl]piperazin-1-yl}methane.

In the title compound, C25H32N4O4, both piperazine rings adopt a chair conformation. One of dioxolane ring systems is essentially planar [dihedral angle = 0.9 (2)°] while the other adopts a slightly disordered envelope conformation, the mean plane of the dioxolane ring being twisted by 3.6 (2)° from that of the benzene ring. The dihedral angle between the benzene rings is 69.9 (5)°. No classical hydrogen bonds were observed.

(E)-N-(1,3-Benzodioxol-5-yl)-1-(4-{[1-(prop-2-en-1-yl)-1H-1,2,3-triazol-4-yl]methoxy}phenyl)methanimine

In the title compound, C20H18N4O3, the dihedral angles between the central benzene ring and the 1H-1,2,3-triazole ring and the fused benzene ring are 65.34 (19) and 3.64 (18)°, respectively. The dioxole ring adopts a shallow envelope conformation, with the methyl­ene C atom displaced by 0.156 (5) Å from the other four atoms (r.m.s. deviation = 0.007Å). In the crystal, the mol­ecules are linked by C—H⋯O and C—H⋯N hydrogen bonds, generating a three-dimensional network.

Ethyl 1′-methyl-2-oxo-4′-[(3aR,5R,5aS,8aS,8bR)-2,2,7,7-tetramethyltetrahydro-3aH-bis[1,3]dioxolo[4,5-b:4′,5′-d]pyran-5-yl]-2H-spiro[acenaphthylene-1,2′-pyrrolidine]-3′-carboxylate

In the title mol­ecule, C30H35NO8, the ace­naphthyl­enone moiety, two atoms of a methyl pyrrolidine ring (N and C atoms) and four atoms of an ethyl acetate moiety (two C and two O atoms) are disordered over two sets of sites in ratio 0.532 (7):0.468 (7). The three C atoms of a di­meth­oxy­ethane ring and dioxolane ring attached with two methyl groups are disordered over two sets of sites in 0.66 (2):0.34 (2) and 0.62 (2):0.38 (2) ratios, respectively. The major and minor components of the ace­naphthyl­ene ring are essentially planar (r.m.s. deviations = 0.0254 and 0.0436 Å, respectively). The major and minor components of the pyrrolidine ring adopt C-envelope conformations with C atoms displaced by 0.492 (11) and 0.595 (7) Å from the remaining ring atoms. One of the dioxolane rings is disordered with its major component in an envelope conformation [C displaced by 0.511 (11) Å] and the minor fraction is more or less planar with an r.m.s. deviation of 0.070 Å. The other dioxolane ring is in an envelope conformation, with a C atom displaced by 0.438 (3) Å from the remainder of the ring atoms. The crystal packing features C—H⋯O inter­actions, which generate C(9) chains.

Methyl 2-(2,2-dimethyl-3a,6a-di-hydro-furo[3,2-d][1,3]dioxol-5-yl)-4-oxo-4H-chromene-3-carboxyl-ate.

In the title mol­ecule, C18H16O7, the dioxolane ring adopts an envelope conformation with the dimethyl-substituted C atom as the flap. The furan ring is almost coplanar with the pyran ring, with a dihedral angle of 1.04 (10)° between the planes, and it makes a dihedral angle of 67.97 (11)° with the mean plane of the dioxolane ring. The latter makes a dihedral angle of 67.15 (10)° with the pyran ring. The O atom attached to the pyran ring deviates by −0.009 (1) Å. The crystal packing features C—H⋯O hydrogen bonds, forming a three-dimensional structure. The meth­oxy­carbonyl atoms are disordered over two positions, with a refined occupancy ratio of 0.508 (18):0.492 (18).

Allyl 2-(2,2-dimethyl-3a,6a-di-hydro-furo[3,2-d][1,3]dioxol-5-yl)-4-oxo-4H-chromene-3-carboxyl-ate.

In the title compound, C20H18O7, the dioxolane ring adopts an envelope conformation with the dimethyl-substituted C atom as the flap, and its mean plane makes a dihedral angle of 73.25 (2)° with the pyran ring mean plane. The furan ring makes dihedral angles of 67.43 (12) and 6.20 (11)° with the mean plane of the dioxolane and pyran rings, respectively. The O atom attached to the pyran ring deviates by 0.0219 (2) Å from its mean plane. In the crystal, mol­ecules are linked via C—H⋯O hydrogen bonds, forming chains along [010] and enclosing R 2 2(9) loops. They stack along the a axis with π–π inter­actions involving the 4H-chromene units [centroid–centroid distances of 3.6389 (13) and 3.6555 (13) Å]. The terminal CH2=CH- atoms of the allyl acetate group are disordered over two sets of sites with a refined occupancy ratio of 0.717 (6):0.283 (6).

The 1,3-dipolar cycloaddition reaction of chiral carbohydrate-derived nitrone and olefin: towards long-chain sugars

The thermal and microwave-activated 1,3-dipolar cycloadditions of several α,β-unsaturated esters derived from d-mannose and chiral nitrones derived from threitol have been studied as a model reaction en route to eleven carbon long chain carbohydrates. Very high facial selectivity is observed for the chiral nitrones whereas the olefin facial selectivity varies with the substrate. The presence of a dioxolane ring α to the olefinic bond is beneficial to the facial selectivity of the olefin whereas a pyranose ring is not. The combination of a d-mannose derivative and a l-threitol-derived nitrone is a matched pair suitable for the synthesis of long chain sugars with nine contiguous chiral centres. Finally complete facial selectivity was observed with exo-glycals which gave a single cycloadduct.

Cyclic Acyloxonium Ions as Diagnostic Aids in the Characterization of Chloropropanol Esters under Electron Impact (EI), Electrospray Ionization (ESI), and Atmospheric Pressure Chemical Ionization (APCI) Conditions

During mass spectrometric analysis of various lipids and lipid derivatives such as the chlorinated counterparts of triacylglycerols, the detailed structure of the characteristic and common ions formed under electron impact (EI), electrospray ionization (ESI), and atmospheric pressure chemical ionization (APCI) conditions by the loss of a single fatty acid remains ambiguous. These ions are designated in the literature as "diacylglyceride ions" and are frequently depicted with a molecular formula without showing any structural features and sometimes represented as cyclic acyloxonium ions. Characterization of these ions is of considerable importance due to their utility in structural identification of lipid derivatives. This study provides complementary evidence on the cyclic nature of "diacylglyceride ions" through the use of the simplest 3-monochloropropanediol diester as a model and the use of isotope labeling technique. Tandem MS/MS studies have indicated that the ion at m/z 135.6 generated from 1,2-bis(acetoyl)-3-chloropropane through the loss of an acetyl group was identical to the ion at m/z 135.6 generated from 4-chloromethyl-2,2-dimethyl-1,3-dioxolane, the latter being generated from a cyclic precursor through the loss of a methyl radical, keeping the dioxolane ring structure intact, thus confirming the cyclic nature of these ions. The corresponding cyclic oxonium ions generated from longer chain chloropropanol diesters, such as the ion at m/z 331.2 originating from 3-monochloropropanediol (3-MCPD) diesters containing palmitic acid(s), could serve as chemical markers for the presence chloropropanol esters.

N,N,N-Trimethyl-N-(methyl 5-deoxy-2,3-O-isopropylidene-β-D-ribofuranosid-5-yl)ammonium 4-methylbenzenesulfonate sesquihydrate

The structure of the title compound, [C12H24NO4][C7H7O3S]·1.5H2O, contains alternating layers parallel to (001) of hydro­phobic and polar character, stabilized by C—H⋯O hydrogen bonding. The furan ring adopts an envelope conformation with the C(OMe) atom as the flap, and the dioxolane ring is twisted about one of the O—C(methine) bonds. A comparison to related compounds is presented. The tosyl­ate-O atoms were disordered over two positions with the major component having a site occupancy factor = 0.566 (12). The structure was refined as a rotary twin with regard to rotation about the c axis with the contribution of the second component being 0.0048 (6). Solvate water mol­ecules are highly disordered and were removed using the SQUEEZE procedure; the unit cell characteristics take into account the presence of the disordered solvent. High-resolution 1H and 13C NMR spectroscopic data are also presented.