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The title compound, C13H13NO2, was prepared by the epoxidation of its racemic precursor. Its structure was determined in order to establish which of two diastereomers would be favored in that reaction and in other reactions of inter­est. The presence of inter­molecular C—H⋯O inter­actions was considered probable, although H-atom positions were not refined. These inter­actions link the mol­ecules into a two-dimensional network.

From reactions between glycolide or lactide (4 equiv.) with 4-dimethylaminopyridine, DMAP (1 equiv.) and NaBPh(4) (1 equiv.) in benzene at 70 degrees C the cyclic ester adducts (CH(2)C(O)O)(6)NaBPh(4) and (CHMeC(O)O)(6)NaBPh(4) are formed respectively. The structures of the salts Na[(S,R,S,R,S,R)-(CH(3)CHC(O)O)(6)](2)BPh(4).CH(3)CN and (CH(2)C(O)O)(6)NaBPh(4).(CH(3)CN)(2) are reported. The cyclic esters were separated by chromatography and the structures of (CH(2)C(O)O)(6), (S,R,R,R,R,R)-(CHMeC(O)O)(6) and (S,S,R,R,R,R)-(CHMeC(O)O)(6) were determined. The (1)H and (13)C NMR data are reported for one of each of the six enantiomers of (CHMeC(O)O)(6) and the two meso isomers. The mechanism for the formation of these 18-membered rings is discussed in terms of an initial reaction between DMAP and NaBPh(4) in hot benzene that produces NaPh and DMAP:BPh(3) in the presence of the monomer lactide. The cyclic esters (CHMeC(O)O)(6) can also be obtained from the reaction between polylactide, PLA, in the presence of DMAP and NaBPh(4). The cyclic esters 3-methyl-1,4-dioxane-2,5-dione and 3,6,6-trimethyl-1,4-dioxane-2,5-dione undergo similar ring enlarging reactions to give cyclic 18-membered ring esters as determined by ESI-MS.

Polar, noncentrosymmetric packing of directional, 1-D hydrogen-bonded networks of chiral, 4-amino-2,6-bis(oxazolinyl)pyridines (ampybox) occurs for isopropyl-substituted ampybox 2; in contrast, 1-D networks of methyl-substituted ampybox 1 pack in an antiparallel arrangement.

The preparation and characterization (IR, 1H, 13C{1H}, 119Sn NMR spectroscopy, elemental analysis and single crystal X-ray structure determination) are reported for Ph3SnOCMe2C(O)OEt (1) and Ph2Sn[OCMe2C(O)NMe2]2 (2). In the solid state, compound 1 contains four-coordinate tin with evidence for incipient bond formation to the ester oxygen: Sn⋯O = 2.648(2) A. Compound 2 contains six-coordinate tin in a pseudo-octahedral geometry. The OCMe2C(O)NMe2 groups form cis-chelates with short, ca. 2.03 A, and long, ca. 2.26 A, Sn–O bonds to alkoxide and amide oxygen atoms, respectively. In solution, compound 1 remains four-coordinate but compound 2 exists as an equilibrium mixture of six-coordinate and five-coordinate species as judged by NMR spectroscopy. At −50 °C in toluene-d8, the six-coordinate isomer is favored and the NMR data are consistent with the structure observed in the solid state. At +50 °C, the NMR data are consistent with a five-coordinate species in which reversible chelation of η2- and η1-OCMe2C(O)NMe2 is fast on the NMR time scale. The molecular structure of 2 and its dynamic solution behavior is proposed to resemble that of Ph2Sn[OCHMeC(O)NMe2]2 formed in the polymerization of L-lactide by Ph2Sn(NMe2)2. The high formation tendency of this compound is proposed to be responsible for the preferential formation of cyclic lactide oligomers (LA/2)n by intrachain transesterification, in contrast to polymerizations employing Ph2Sn(OPri)2, which produce long chains of H–(LA/2)n–OPri where LA = [OCHMeC(O)OCHMeC(O)]. The kinetics of the reactions between Ph3SnX and each of Me2CHC(O)OMe, Me(MeO)CHC(O)OEt and Ph3SnOCHMeC(O)OEt, have been determined from NMR studies in benzene-d6 where X = NMe2 or OPri. Similarly, the reaction between Ph3SnOBut and (p-tolyl)3SnOPri has been followed. The former reactions represent transamidation and transesterification, and the latter models chain transfer. These findings, when compared to the earlier studies of the ring-opening of lactide and its subsequent ring-opening polymerization, indicate that the rate follows the order: chain transfer > ring-opening > ring-opening polymerization > transesterification, although the latter is influenced by the ester end-group.

The crystal structure of the title compound, C20H17NO4S, (I), was determined in order to compare the solution and solid-state conformations. The mol­ecule was synthesized as a building block for incorporation into oligosaccharides comprised of conformationally restricted furan­ose residues. The furan­ose ring adopts an envelope conformation with the ring O atom displaced above the plane (an OE conformation). The pseudorotational phase angle (P) is 88.6° and the puckering amplitude (τm) is 31.5°. The C2—C1—S—C(Ph) torsion angle is −163.2 (2)°, which places the aglycone in the exo-anomeric effect preferred position. The C1—S—C14 bond angle is 99.02 (13)° and the plane of the cresyl moiety is oriented nearly parallel to the four in-plane atoms of the furan­ose ring envelope. The orientation about the C4—C5 bond is gauche–gauche [Bock & Duus (1994). J. Carbohydr. Chem. 13, 513–543].

The synthesis and characterization of a new cobalt(II) complex [Co(Me2H2Me2malox)(py)2][Me2H2Me2malox = 4,4′-oxalyldinitrilodi(pent-2-en-2-olato)(2–), py = pyridine], based on a chelating ligand containing no saturated chelate rings, is described together with the corresponding cobalt(III) complex. The cobalt(II) complex binds dioxygen in a reversible manner in pyridine solution at temperatures near –20 °C. The corresponding copper(II) complex [Cu(Me2H2Me2Me2malox)] crystallizes in the monoclinic system P21/c with a= 8.866(1), b= 16.029(1), c= 9.106(1)A, β= 97.57(2)° and Z= 4. Structural refinement resulted in R= 0.0423 and R′= 0.0436 for 2153 observed reflections. Studies of [Cu(Me2H2Me2malox)] using X-ray crystallography and IR spectroscopy guided the development of the synthetic procedure used in the isolation of the cobalt(II) adduct. A six-co-ordinate cobalt(III) complex is reported as a model for the cobalt–dioxygen adduct. Proton exchange with solvent has been observed using NMR spectroscopy and implications for the rational design of dioxygen carriers is discussed.

Ba(ClO4)2.3H2O, Mr = 390.28, hexagonal, P63/m, a = 7.277 (2), c = 9.656 (1) A, V = 442.9 (1) A3, Z = 2, F(000) = 368, D chi = 2.93 g cm3, lambda(Mo K alpha) = 0.71069 A, T = 295 K, mu = 52.60 cm1, 456 unique reflections, R = 0.023. The barium atoms in this structure are coordinated by six water oxygens, O(3), at 2.919 (1) A and by six perchlorate oxygens, O(2), at 3.026 (2) A in a slightly distorted icosahedral arrangement, the average Ba-O separation thus being approximately 2.97 A. The perchlorate ion just fails to have regular tetrahedral geometry within the experimental error, and has an average Cl-O bond length of 1.433 (6) A. Consistent with hydrogen bonding delineated on the basis of least-squares-refined hydrogen-atom positions, each axial [O(1)] perchlorate oxygen is hydrogen bonded to three water molecules and each trigonal [O(2)] perchlorate oxygen is hydrogen bonded to two water molecules; thus each perchlorate ion is hydrogen bonded to nine water molecules. Conversely, each water molecule [O(3)] oxygen is hydrogen bonded to six perchlorate ions to two through axial [O(1)] oxygens and to four through trigonal [O(2)] oxygens.

Etude structurale des complexes dichlorure de bis-(η 5 -tricyclo [5.2.1.0 2,6 ] decatriene-2,5,8yl-6)M (M=Zr, Ti)

The optical isomers and deoxy form of 2-(3,4, alpha-trihydroxybenzyl)imidazoline hydrochloride were examined for their alpha-adrenergic activity on rat aorta. The rank order of stimulant activity was deoxy (2) congruent to (R)-(-)-1 greater than (S)-(+)-1. This is in contrast to catecholamines in which the order of activity is (R)-(-)-epinephrine greater than (S)-(+)-epinephrine = epinine (deoxyepinephrine). The relative order of potency for the isomers of 2-(3,4, alpha-trihydroxybenzyl)imidazoline is different than that predicted by the Easson--Stedman theory for stereoisomers of catecholamines. Also, substitution of the deoxy compound 2 with substituents, methyl or benzyl, in the 4-position lowers the alpha-adrenergic agonist activity, and differences observed between optical isomers were small.

Synthesis and antileukemic activity in vivo of the four diastereomeric 1-hydroxy-3,4-diaminocyclohexane-Cl2PtII complexes (Cl2PtII-3a-d) are described. Respective bis(phenylmethyl) (1 alpha,2 alpha,4 beta)-, (1 alpha,2 alpha,4 alpha)-, (1 alpha,2 beta,4 beta)-, and (1 alpha,2 beta,4 alpha)-(4-hydroxy-1,2-cyclohexanediyl)bis(carbamates) (5a, 5b, 7a, 7b) were prepared by hydroboration-oxidation of the bis(carbobenzoxyamino) derivatives (4,5) of cis- and trans-4,5-diaminocyclohexene. The relative stereochemistry of intermediates 5a and 5b was established by correlation with the alcohol obtained by NaBH4 reduction of bis(phenylmethyl) (1 alpha,2 alpha,3 alpha,4 alpha)-(3,4-epoxy-1,2-cyclohexanediyl)bis(carbamate) (8), the all-cis stereochemistry of which was unambiguously determined by X-ray crystallographic analysis. In the P-388 murine leukemia model these monohydroxycyclohexanediamine-PtII complexes were more effective than the PtII complexes of the related diol diamines 1a-e but were less active than the cisplatin positive control.

The dianion of (S)-ethyl β-hydroxybutyrate (1) was treated with N -trimethylsilyl Imine 2 to afford β-lactam 4. The same dianion reacted with N -ary1 imine 10 to give β-lactams 11, 12, and 13. A three-step sequence was used to convert 4 into the β-lactam-pyran hybrid 9 while a five-step sequence was developed to transform 11 and 12 into 9. Application of the carboxyinversion reaction to derivatives of 9 afforded protected analogs of the amino-saccharldes daunosamlne (5) and acosamine (6).

Reaction of trimethylsilyl enol ether6 with buffered m -chloroperbenzoic acid at 20°C leads efficiently to7, the first shelf-stable silyloxy epoxide. The structural dimensions of7 have been ascertained by means of X-ray crystallography.

Cristallisation dans P1 avec affinement jusqu'a 0,029. La structure consiste en empilements d'atomes de Ni de coordination octaedrique et d'ions perbromates de geometrie tetraedrique, relies par liaison hydrogene

Etude des reactions d'insertion de N-sulfinylsulfonamides et de bis(sulfonylimide) soufre dans les liaisons σ metal-carbone de CpFe(CO)(L)Me (L=PPh 3 ,P(OPh) 3 ). Etude RX de la structure de CpFe(CO) 2 {S[NS(O) 2 Me](O)CH 2 Ph}•1/2CH 2 Cl 2

The crystal structure of syn-[4.4.3]propella-2,4,12-trien-11-ol 3,5-dinitrobenzoate, 2, has been determined by single crystal X-ray diffraction and refined to an R value of 0.051. The crystal structure is triclinic with a = 10.208(2), b = 13.355(2), c = 7.068(1) Å, α = 99.35(1)°, β = 100.63(1)°, γ = 100.79(1)°, and the space group is [Formula: see text] with two molecules per cell, D(calcd) = 1.39 g cm−3. The unsaturated five-membered ring resides in an envelope conformation with C6—C11—C12—C13 lying essentially in a plane. The fifth atom, C1, is positioned 0.47 Å out of this plane on the side opposite O1. The latter is situated 1.38 Å away and projects the 3,5-dinitrobenzoate group above the central portion of the cyclohexadiene unit. Four contiguous carbon atoms in the latter ring are mutually coplanar and the fused cyclohexane ring adopts a chair conformation. The overall molecular geometry is reconcilable with its solvolytic behavior in aqueous acetone.

Le stereoisomere dl cristallise dans le systeme orthorhombique, groupe P2 1 2 1 2 1 et le stereoisomere meso dans le systeme monoclinique, groupe P2 1 /n. Affinement jusqu'a R=0,027 et 0,026 respectivement

Synthese d'hexahydro-2,3,3a,6,7,7a epoxymethano-7,3a indenones-9 et d'octahydro-1,2,4a,5,6,7,8,8a epoxymethano-1,4a naphtalenones-10 a partir d'acides benzoiques et d'hydrocarbures bromes via des iodo-8 oxa-6bicyclo [3.2.1] octene-2ones-7

Methyl dodecahedranecarboxylate, C22H22-O2, (4), Mr = 318.42, monoclinic, C2/c, a = 12.600 (2), b = 7.992 (4), c = 28.975 (7) A, beta = 101.79 (2) degrees, V = 2856 A3, Z = 8, Dx = 1.48 g cm-3, lambda(Mo K-alpha) = 0.71073 A, mu = 0.84 cm-1, F(000) = 1360, T = 294 K, R = 0.044 for 2109 unique reflections with Fo2 greater than 3 sigma(Fo2). 21-Phenylcyclopropadodecahedrane, C27H24, (5), Mr = 348.49, tetragonal, P4(2)/n, a = 17.528 (3), c = 10.752 (2) A, V = 3303 A3, Z = 8, Dx = 1.40 g cm-3, lambda(Mo K-alpha) = 0.71069 A, mu = 0.85 cm-1, F(000) = 1488, T = 295 K, R = 0.053 for the 1773 unique reflections with Fo2 greater than 1 sigma(Fo2). The molecular geometries of methoxycarbonyldodecahedrane (4) and 21-phenylcyclopropadodecahedrane (5) are compared to those of the parent C20H20 hydrocarbon (1) and its 1,16-dimethyl derivative (2). For both (2) and (4), the framework is modestly distorted by the substituents, the intracavity distance being more extended along the axis that contains the pendant group(s). Remarkably for (5), its cyclopropane ring has all C-C bonds and internal angles essentially equal, and those dodecahedrane bonds in the immediate vicinity of the ring fusion are extensively perturbed.

The unparalleled substituent-dependent regulation of the course of cycloaddition reactions between isodicyclopentadienes and tropones is described.

L'etude est faite sur les composes suivants: tetrahydro-4',5',6',7' spiro [cyclopropane-1:8'-methano-4',7'indene], dimethyl-2',2' tetrahydro-4',5',6',7' spiro [cyclopropane-1:8'-methano-4',7'indene] et spiro [cyclopropane-1:8'-methano-4,7 benzo [c] furanne

Structures cristallines et moleculaires des deux stereoisomeres Rn, Sn- et Sn, Sn-. La plus importante difference structurale entre les deux structures est la position des cycles phenyle par rapport au cœur Pt-P-Pt-P