Synthesis of enantiopure cis-decahydroquinolines from homotyramines by Birch reduction and aminocyclization

Birch reduction of homotyramines with a syn-β-amino alcohol unit followed by acid treatment of formed dihydroanisole derivatives gives polysubstituted enantiopure cis-decahydroquinolines. The stereoselectivity of the process differs if the hydroxyl group is free or protected. The procedure allows the synthesis of 7-oxodecahydroquinolines embodying four stereogenic centres with the same relative configuration as that of lepadins F and G.     

Coeffective and de Rham cohomologies of symplectic manifolds

We discuss the relation of the coeffective cohomology of a symplectic manifold with the topology of the manifold. A bound for the coeffective numbers is obtained. The lower bound is got for compact Kähler manifolds, and the upper one for non-compact exact symplectic manifolds. A Nomizu's type theorem for the coeffective cohomology is proved. Finally, the behaviour of the coeffective cohomology under deformations is studied.     

Crystal and molecular structure of (+)-6,7∶8,9∶10,11-tri-O-isopropylidene-2,3-dideoxy-d-arabino-l-allo-undec-2-enono-1,4-lactone,C20H30O9

The crystal structure of the title lactone, C₂₀H₃₀O₉, a potential precursor of uncommon 11-carbon sugar derivatives, has been determined by single-crystal diffraction methods. The compound crystallizes in the orthorhombic space groupP2₁2₁2₁ witha=15.581(3),b=14.047(2),c=9.888(2) Å, andZ=4. The structure was solved by direct methods and refined by full-matrix least-squares toR=0.054. The absolute configuration of the seven stereogenic carbon atoms was deduced as 4R, 5R, 6R, 7R, 8S, 9R, 10R, being (R)-(+)-glyceraldehyde its progenitor. An intramolecular O-HO hydrogen bond is present. Weak interaction C-HO links the molecules in sheets parallel to the (100) plane.     

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,=96.66(2)°, andZ=2. A total of 1055 reflection intensities were recorded on a Siemens AED single-crystal diffractometer (CuK 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 2(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-HO hydrogen bond joins the molecules in chains which run along the twofold screw axis.     

Oxidative DNA damage induced by autoxidation of microquantities of S(IV) in the presence of Ni(II)-Gly-Gly-His

NiIIGGH (GGH = glycylglycylhistidine) reacts rapidly with S(IV), in air-saturated solution, to produce NiIIIGGH. A mechanism is proposed where initial NiIII oxidizes SO3(2-) to SO3*-, which reacts with dissolved oxygen to produce SO5*-, initiating radical chain reactions. DNA strand breaks and 8-oxo-7,8-dihydro-2'-deoxyguanosine formation were observed in air-saturated solutions containing micromolar concentrations of Ni(II) and S(IV). The extent of DNA damage showed dependence on the ratio of the NiIIGGH : S(IV) concentrations and the ionic strength.     

Computer-aided design of chiral ligands. Part 2. Functionality mapping as a method to identify stereocontrol elements for asymmetric reactions

A computational method to determine the energetically favorable positions of functional groups with respect to the transition states of stereoselective reactions based on force field energy minimization is presented. The parameters of this functionality mapping, the characteristics of the target transition states, and the features of the probe structures are outlined. Our method was found to reproduce the positions of the stereodiscriminating fragments for some known chiral ligands including the Masamune dimethylborolane, dimenthylborane, the Corey stien reagent, the Roush allylboronate tartrates, and the secondary amine Diels-Alder catalysts described by MacMillan. Functionality mapping can be used to better understand the specific interactions in the transition states leading to the products by providing a quantitative measure of the stabilization/destabilization afforded by the different ligand components via nonbonded interactions. The method can determine if a chiral ligand imparts the observed selectivity by stabilizing one reaction pathway, by destabilizing a reaction pathway, or by a combination of both. Orientational as well as positional information about potential functional groups is readily obtained. In addition to its utility as an analytical tool, functionality mapping can be used to explore starting points for the design of new chiral ligands.     

δ-Santalolanaloga I Synthesen in der Isocamphanreihe, 27. Mitt.

The synthesis of 4-(3,3-dimethyl-2-exo-norbornyl)-2-methyl-2-buten-1-ol (5), an analogue of -santalol (1) has been described. One route to5 starts with isocamphenilanyl propionic acid (8) which can be prepared in 4 steps from isocamphenilanic acid (9). Also 4 steps lead from8 to the target molecule5 with an overall yield of 24%. By a second and more convergent route, starting from the very easily obtainable bicyclic ketone19, the allylic alcohol5 could be obtained again in 4 steps, but this time with an overall yield of 1.3%. A new and easy synthesis of isocamphenilanyl acetic acid (15), a potential starting material to5, has been described, also the preparation of some new isocamphane derivatives.

26. Mitt:Buchbauer G,Pernold W,Ittner M,Ahmadi MF,Dobner R,Reidinger R (1985) Monatsh Chem 116: 1209