Search results for "stereochemistry"

The Introduction of Substituents into the Pyridine Ring

1964

Generation of Stereocenters Around a C3-Symmetric Cyclotriveratrylene Crown

2012

The oxidation of racemic methylthio-substituted C3-symmetric cyclotriveratrylene (CTV) 2 produces the corresponding trisulfoxides 3 as follows. Oxidation with m-chloroperoxybenzoic acid (m-CPBA) in dichloromethane leads to the formation of a distribution of the four possible diastereomers that is relatively close to the statistical outcome, in which the C3-symmetric stereoisomers are the minor species. In contrast, the optically active Davis reagent [oxaziridine (+)-4] in carbon tetrachloride at room temperature leads to a biased (73 %) distribution in favor of the C3-symmetric MRRR/PSSS diastereomer of 3 with 56 % ee (PSSS enantiomer according to the model of Davis). Interestingly, when th…

Ultrasound assisted reductive cleavage of sesquiterpene γ-enonelactones

1995

Abstract Ultrasound enhances the rate of reductive cleavage of the C 6 -oxygen bond of several cis - and trans - sesquiterpene γ-enonelactones. Interestingly ultrasound overrides the stereoelectronic requirements for the reductive cleavage of the most usually occurring sesquiterpene trans -lactones.

Seven-, Eight-Membered and Larger Heterocyclic Rings and Their Fused Derivatives

2015

ChemInform Abstract: Total Synthesis of (.+-.)-Scopolamine: Challenges of the Tropane Ring.

2016

Scopolamine was synthesized using 6,7-dehydrotropine as a key intermediate. Rhodium-catalyzed [4 + 3] cycloaddition chemistry and a modified Robinson–Schopf reaction were each independently evaluated for their utility in constructing the tropane core. Both synthetic approaches gave comparable overall yields.

catena-Poly[benzyltriethylammonium [tri-μ-thiocyanato-κ4N:S;κ2S:N-cadmate(II)]]

2006

The title compound, {[(C6H5CH2)N(C2H5)3][Cd(SCN)3]}n, contains benzyl­triethyl­ammonium cations lying between one-dimensional chains of stoichiometry {[Cd(SCN)3]−}n. Each Cd2+ ion is 3N,3S-hexa­coordinated by thio­cyanate ligands in an octa­hedral arrangement. The asymmetric unit contains one cation and one anion.

ChemInform Abstract: 1,2,4-Oxadiazole Rearrangements Involving an NNC Side-Chain Sequence.

2010

The thermal rearrangement of N-1,2,4-oxadiazol-3-yl-hydrazones into 1,2,4-triazole derivatives is reported. This represents the first example of a three-atom side-chain rearrangement involving an NNC sequence linked at the C(3) of the oxadiazole. The reactions carried out under solvent-free conditions produced good to high yields of the final products.

The inhibition by naphthoquinones and anthraquinones of 2-amino-3-methylimidazo[4,5- f  ]quinoline metabolic activation to a mutagen: a structure-act…

1998

Nine naphthoquinones, 19 anthraquinones, and nine structurally related monoketonic compounds such as anthrone, xanthone, etc., inhibited mutagenicity induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in Salmonella typhimurium TA 98 in the presence of rat liver S9 with distinct structure-activity relationships. A carbonyl function was a prerequisite for antimutagenicity while, in general, anthraquinones (IC50 values: 2.3–>213 nmol/ml top agar) were more potent antimutagens than structurally related monoketonic compounds (IC50 values: 25.3–94.9 nmol/ml top agar) and naphthoquinones (IC50 values: 3.7–90.7 nmol/ml top agar). The parent compounds and methyl substituted derivatives were alr…

Two isorhamnetin triglycosides from Anthyllis sericea

1989

Abstract A fraction of a methanolic extract of aerial parts of Anthyllis sericea yielded vicenin 2 and the two new compounds isorhamnetin 3- O -(2- O -β-glucopyranosyl-6- O -α-rhamnopyranosyl)-β-galactopyranoside and isorhamnetin 3- O -(2- O -β-glucopyranosyl)-βl-galactopyranoside-7- O -β-glucopyranoside.

New diterpenes from Sideritis sicula

1978

Abstract Two new diterpenes have been isolated from Sideritis sicula : sideripol, ent -18-acetoxy-7α-hydroxykaur-15-ene and epoxysideritriol, ent -15β,16β-epoxykauran-7α,17,18-triol. The previously known diterpene eubol, ent -7α-acetoxykaur-16-en-15β,18 diol has also been obtained from the same source.