Marisa Ferrari Belicchi

The four-carbon elongation of three-carbon chiral synthons using 2-(trimethylsiloxy)furan: highly stereocontrolled entry to enantiomerically pure seven-carbon α,β-unsaturated 2,3-dideoxy-aldonolactones

Abstract The BF3-promoted addition of 2-(trimethylsiloxy)furan to three carbon synthons derived from D- and L-glyceraldehyde, D- and L-serinal, and imines thereof furnishes C7 α,β-unsaturated 2,3-dideoxy-aldonolactone derivatives in high yield, with very high level of diastereoselection. In all the cases, compounds having 4,5-threo:5,6-erythro relative stereodisposition preferentially emerge from the reactions, accompanied by only marginal amounts of 4,5-erythro:5,6-erythro epimers. An empirical rule for the rapid assigment of the configuration at C-4 (γ-carbon) of γ- substituted unsaturated and saturated γ-butyrolactones is given, based upon the sign of the optical rotation values.

2,3-Unsaturated C-glucopyranosides: A guideline to the anomeric configurational assignment

Abstract Contrary to a previous reporte, the SnCl 4 -promoted arylation of tri-O-acetyl-D-glucal( 1 ) by means of anisole ( 2 ) gives rise to 1′-(4,6-di-O-aceyl-2,3-dideoxy- β -D-erythro-hex-2-enopyranosyl)-4′-methoxybenzene ( 3 ) and not α-anomer ( 4 ). A guideline to the correct assignment of the anomeric congiguration of 2,3-unsaturated C -glucopyranosides is suggested, which violates the Hudson isorotation rule.

Stereoselective arylation of pyranoid glycals, using bromomagnesium phenolates: An entry to 2,3-unsaturated C-α-glycopyranosylarenes

Abstract The arylation of acetylated pyranoid glycals at C-1 by means of bromo-magnesium phenolates provides a highly stereoselective entry to 1- C -α-glycopyranosyl-2-hydroxyarenes.

Synthesis and X-ray structures of dinitrato-bis[2-(2′-thienyl)-1-(2′-thienylmethyl)benzimidazole]copper(II) and dichloro-bis-[2-(2′-thienyl)-benzimidazole]copper(II)-ethanol

SummaryThe reactions of Cu(NO3)2 · 3 H2O with 2- (2′-thienyl)-1-(2′-thienylmethyl)benzimidazole (L′) and of CuCl2 · 2H2O with 2-(2′-thienyl)benzimidazole (L) have been carried out. The crystal structure of two isolated complexes,(1) and(2), have been determined by single-crystal x-ray diffraction methods. Crystals of(1) are monoclinic, space groupP21/c, witha=9.884(4),b=9.892(4),c=18.732(8) Å, β=114.89(2)°,Z=2;R=0.068 for 1909 “observed” reflections. Crystals of (2) are orthorhombic, space groupPbcn, witha=14.835(1),b=8.193(1),c=20.493(1) Å,Z=4;R=0.086 for 415 “observed” reflections. In the complex (1) the copper co-ordination is tetragonal (compressed octahedral) and involves a nitrogen atom of the organic ligand [Cu-N 1.970(6) Å] and two oxygen atoms of the nitrate group [Cu-O 2.318(7) and 2.246(9) Å] which appears to coordinate nearly symmetrically to the metal; however it has unusually large thermal motion which suggests a fluxional behaviour. In the complex (2) the co-ordination is square planar and involves an imidazole nitrogen [Cu-N 1.95(3) Å] and a chlorine atom [Cu-Cl 2.27(1) Å]. A long interaction Cu-S=3.37(2) Å completes the co-ordination polyhedron to a very elongated distorted tetragonal bipyramid. In both compounds a thiophene ring is disordered.

A highly stereoselective route to 1-C-(2-hydroxyaryl)-alditol derivatives

Abstract Arylation at C-1 of 2,3:4,5-di- O -isopropylidene- d -arabinose and 4- O -benzyl-2,3- O -isopropylidene- d -threose variously using titanium or magnesium salts of 4- tert -butylphenol, 2-naphthol, and 5-pentylresorcinol gave the epimeric 1- C -aryl-alditol derivatives. One of these derivatives, namely, 1- C -(3- tert -butyl-6-hydroxyphenyl)-2,3:4,5-di- O -isopropylidene- d - gluco -pentitol, forms a crystalline 1:3 inclusion compound with 4- tert -butylphenol, the structure of which, established by X-ray diffraction, shows that guest molecules are linked through hydrogen bonds to the hydrophilic cavity created by the helical chains of the hosts.

Crystal and molecular structure of (−)-1,2-O-isopropylidene-3-O-methyl-7,8-dideoxy-β-l-glycero-d-gluco-non-7-enofuranurono-9,6-lactone, C13H18O7

The crystal structure of the title lactone, C13H18O7, has been determined by single crystal diffraction methods. The compound crystallizes in the monoclinic space groupP21 witha=13.231(2),b=10.248(2),c=5.348(1) Å,β=96.66(2)°, andZ=2. A total of 1055 reflection intensities were recorded on a Siemens AED single-crystal diffractometer (CuKα radiation) at room temperature. The structure was solved by direct methods and electron density calculations. Full-matrix least-squares refinement gaveR=0.055 for 946 unique reflections above 2σ(I). The absolute configuration of the six chiral carbon atoms was deduced as 4S, 5R, 6R, 7S, 9R, 10R (crystallographic numbering corresponds to C-6, 5, 4, 3, 2, 1 in the title compound). An intermolecular O-H⋯O hydrogen bond joins the molecules in chains which run along the twofold screw axis.

Highly stereocontrolled substitution of phenols with pyruvic esters. A viable route to ortho-hydroxyatrolactic esters of (2R)- and (2S)-configuration

Abstract Treatment of phenols with optically active (+)- and (−)-menthyl pyruvate assisted by Al(III)- or Ti(IV)-based promoters leads to the formation of ortho -hydroxyatrolactic esters of (2R)- and (2S)-configuration. The use of suitable menthol-based promoters augments markedly (up to 96% d.e.) the intrinsic stereochemical bias of the chiral pyruvate.

Synthesis and X-ray structure of the tetrameric molybdenum complex [C16H13N2S2]+2[Mo4Cl4O8(OEt)4]2–

The reactions of MoCl5 with 2-(2′-thienyl)benzimidazole (I) and 2-(2′-thienyl)-1-(2′-thienylmethyl)benzimidazole (II) have been carried out. From the reaction of (I) a molybdenum complex was obtained, which surprisingly was found to contain (II), by X-ray diffraction analysis. Crystals of the complex are triclinic, space group P, with unit-cell dimensions, a= 10.524(2), b= 14.352(4), c= 10.213(2)A, α= 95.49(1), β= 100.68(3), γ= 118.79(1)°, Z= 1, and R= 0.076 for 2 129 observed reflections. The structure has been solved by direct methods and refined by least squares. It consists of centrosymmetric tetramers, [{MoClO2(OEt)}4]2–, surrounded by 2-(2′-thienyl)-1-(2′-thienylmethyl)benzimidazolium cations linked to the tetramers through O ⋯ HN+ bridges.

Bis(L-phenylalaninamidato)copper(II): crystal structure and enantioselectivity

Bis(L-phenylalaninamidato)copper(II)(2), whose crystal structure is reported, when added to the eluant, is able to perform chiral resolution of D,L-dansyl-amino acids in h.p.l.c. (reversed phase).

Synthesis and spontaneous resolution by crystallization of R,S-(±)-dimethyl(1-methyl-2-oxo-2-phenylethyl)sulphonium bromide. X-Ray structure and absolute configuration of the R-enantiomer

R,S-(±)-Dimethyl(1-methyl-2-oxo-2-phenylethyl)sulphonium bromide (3a), obtained from 1-phenylpropanone by bromination with t-buty bromide–dimethyl sulphoxide and further reaction with dimethyl sulphide, undergoes spontaneous resolution of its two enantiomers upon crystallization, as demonstrated by a single crystal X-ray analysis and assignment of absolute configuration (R).