Electron Transfer-oxy Radical Mechanism for Anti-cancer Agents: 9-anilinoacridines

A possible mode of action involving electron transfer is advanced for the 9- anilinoacridines. The mechanism entails formation of toxic oxy radicals which destroy the neoplasm. Cyclic voltammetry was performed on iminium type ions derived by protonation of the acridines. Reductions were generally reversible with potentials of about - 0.60 V. Involvement of quinoidal metabolites is also a possibility. The relationship of electrochemical behavior to structure and physiological activity is addressed

Kinetic Resolution in Asymmetric Epoxidation using Iminium Salt Catalysis

The first reported examples of kinetic resolution in epoxidation reactions using iminium salt catalysis are described, providing up to 99% ee in the epoxidation of racemic cis-chromenes

Types and properties of metal-free catalysts for living polymerizations of biomaterials

Syntéza biokompatibilních a biodegradabilních polyesterů, použitelných převážně v medicíně, využívá pro polymeraci za otevření kruhu katalyzátory na bázi kovu (např. Sn, Al atd.), které se mohou po implantaci deponovat v těle. Podstatou bakalářské práce je popis netoxických "metal-free" karbenových sloučenin a jejich vlastností použitelných jako katalyzátory pro polymeraci cyklických esterů. Příprava těchto stabilních karbenových katalyzátorů a jejich charakterizace je cílem experimentání práce.Synthesis of biocompatible and biodegradable polyesters applicable mainly in biomedicine uses metal catalysts (based on Sn, Al etc.) for ring opening polymerization, which could be deposited in a body after implantation. Objective of the bachelor thesis is description of non-toxic metal-free carbene compounds and their properties utilizable as catalysts for polymerization of cyclic esters. Preparation of these stable free carbene catalysts and their characterization is the main goal of the experimental work.

Charge Transfer-oxy Radical Mechanism for Anti-cancer Agents

The proposal is advanced that anti-cancer drugs generally function by charge transfer resulting in formation of toxic oxy radicals which destroy the neoplasm. Electrochemical studies were performed with some of the main types of agents: iminium ions (adenine iminium from alkylating species, iminium metabolite of 6-mercaptopurine, nitidine, other polynuclear iminiums) and metal complexes (Pt(II)diaquodiammine-guanosine, copper salicylaldoximes). Reduction potentials ranged from -0.4 to -1.2 V. Literature data for quinones are presented and radiation is discussed. Based on the theoretical framework, a rationale is offered for the carcinogen-anti-cancer paradox and the role of antioxidants

Kinetics and mechanism of organocatalytic aza-Michael additions: direct observation of enamine intermediates.

The imidazoles 1a–g add to the CC-double bond of the iminium ion 2 with rate constants as predicted by the equation log k = sN(N + E). Unfavourable proton shifts from the imidazolium unit to the enamine fragment in the adduct 3 account for the failure of imidazoles to take part in iminium-activated aza-Michael additions to enals

Counterion effects in iminium-activated electrophilic aromatic substitutions of pyrroles.

Electrophilic substitution of pyrroles by a,b-unsaturated iminium ions is slow in acetonitrile when only weakly basic counterions are present. When the reactions are carried out in the presence of KCF3CO2, fast deprotonation of the intermediate r-adducts occurs, and the rate constant for the rate-determining CC bond-forming step can be predicted from the electrophilicity parameter E of the iminium ion and the N and s parameters of the pyrroles

Total Synthesis and Structural Revision of the Alkaloid Incargranine B

Seeing double: Consideration of the biosynthetic origins of incargranineB, which was originally assigned an unprecedented indolo[1.7]naphthyridine structure, led to the proposal of a dipyrroloquinoline framework as a more biosynthetically feasible struct

The alpha-effect in cyclic secondary amines: new scaffolds for iminium ion accelerated transformations

Five-membered secondary amine heterocycles containing an α-heteroatom were prepared and shown to be ineffective as catalysts for the iminium ion catalysed Diels–Alder reaction between cinnamaldehyde and cyclopentadiene. Their six-membered counterparts proved to be highly active catalysts. In stark contrast, the catalytic activity observed when comparing the non α-heteroatom cyclic amines proline methyl ester and methyl pipecolinate showed the five-membered ring amine was significantly more active. Concurrent density functional theoretical calculations suggest a rationale for the observed trends in reactivity, highlighting that LUMO activation through an iminium ion intermediate plays a key role in catalytic activity