Biomedical subjects

Vered Marks

Publications and source records attributed to Vered Marks.

5 recordsLinked to original sources

PubMed2007

1,3-dipolar cycloadditions of trimethylsilyldiazomethane revisited: steric demand of the dipolarophile and the influence on product distribution.

The 1,3-dipolar cycloaddition of trimethylsilyldiazomethane with alpha,beta-unsaturated esters was examined. The resulting 1-pyrazolines isomerize to regioisomeric 2-pyrazolines (a or b) or undergo desilylation (c). Acrylates yield only b or c. beta-Substituted dipolarophiles may yield all three types of products. This work demonstrates that the distribution of 2-pyrazoline products is highly dependent on the relative configuration of the substituents on the 1-pyrazoline intermediate.

Cyclization↗

PubMed2006

Novel carboxylated pyrrole- and carbazole-based monomers. Synthesis and electro-oxidation features.

Carboxylated pyrrole (Pyr, a index)- and carbazole (Cbz, b index)-containing monomers 6-7a/b and 9a/b have been readily synthesized from the monobenzyl ester of L-glutamic acid and triamine 2 using Clauson-Kaas and amide coupling reactions. In contrast to Pyr-containing compounds 6-7a, and 9a, the three Cbz-containing monomers 6-7b, and 9b have been found electroactive and were successfully electropolymerized on a Pt electrode resulting in the deposition of corresponding insoluble electroconducting polyCOOH polyCbz-films poly(6-7b) and poly(9b).

Carbazoles↗

PubMed2003

Dynamic and static conformational analysis of acylated tetrahydrobenzazepines.

A detailed high-field NMR analysis of several acylated tetrahydrobenzazepines, supported by molecular mechanics calculations, indicates that the heterocyclic ring in these compounds exists in a chair conformation, with the carbonyl oriented anti to the aryl moiety in the dominant rotamer. Surprisingly, ring methylenes are typically diastereotopic at room temperature, as the barriers for the process of enantiomerization of the seven-membered ring are much higher than expected. It is shown that ring inversion is correlated (but not concerted) with rotation of the amide moiety, as the carbonyl is forced out of conjugation with the nitrogen in the transition state.

Journal Article↗

PubMed2003

Crystal structure and rotational barrier of octakis(bromomethyl)naphthalene.

Octakis(bromomethyl)naphthalene (4) adopts in the crystal a chiral conformation with a helical central naphthalene core and the bromomethyl groups disposed in an alternate up-down "in" arrangement. According to MM3 calculations, this conformation is less stable than the corresponding all alternated "out" form, while B3LYP/LANL2DZ calculations suggest the opposite stability order. The topomerization barrier (16.0 kcal mol(-1)) is ascribed to an enantiomerization process requiring 180 degrees rotation of all the bromomethyl groups and reversal of the helical sense of the naphthalene core.

Journal Article↗

PubMed2002

Polyethylated triptycene derivatives.

The octaethyl triptycenes 7 and 8 were synthesized by Diels-Alder reaction of the octaethylanthracene 4with the corresponding benzynes. Low-temperature NMR spectra of 7 and 8 are consistent with the presence of the fully alternated conformation "a" of C(2) symmetry. However, in the determined crystal structures, the compounds adopt a higher energy conformation with a pair of vicinal ethyls oriented in the same direction.

Journal Article↗