Profound Methyl Effects in Drug Discovery and a Call for New C?H Methylation Reactions

The methyl group is one of the most commonly occurring carbon fragments in small‐molecule drugs. This simplest alkyl fragment appears in more than 67 % of the top‐selling drugs of 2011 and can modulate both the biological and physical properties of a molecule. This Review focuses on so‐called magic methyl effects on binding potency, where the seemingly mundane change of C? H to C? Me improves the IC₅₀ value of a drug candidate more than 100‐fold. This discussion is followed by a survey of recent advances in synthetic chemistry that allow the direct methylation of C(sp²)? H and C(sp³)? H bonds. It is our hope that the relevance of the meager methyl group to drug discovery as presented herein will inspire reports on new C? H methylation reactions.     

5-Aminolevulinic acid and its derivatives: physical chemical properties and protoporphyrin IX formation in cultured cells

Protoporphyrin IX (PpIX) is used as a fluorescence marker and photosensitizing agent in photodynamic therapy (PDT). A temporary increase of PpIX in tissues can be obtained by administration of 5-aminolevulinic acid (ALA). Lipophilicity is one of the key parameters defining the bioavailability of a topically applied drug. In the present work, octanol-water partition coefficients of ALA and several of its esters have been determined to obtain a parameter related to their lipophilicity. The influence of parameters such as lipophilicity, concentration, time, and pH value on PpIX formation induced by ALA and its esters is then investigated in human cell lines originating from the lung and bladder. ALA esters are found to be more lipophilic than the free acid. The optimal concentration (c(opt), precursor concentration at which maximal PpIX accumulation is observed) is then measured for each precursor. Long-chained ALA esters are found to decrease the c(opt) value by up to two orders of magnitude as compared to ALA. The reduction of PpIX formation observed at higher concentrations than c(opt) is correlated to reduced cell viability as determined by measuring the mitochondrial activity. Under optimal conditions, the PpIX formation rate induced by the longer-chained esters is higher than that of ALA or the shorter-chained esters. A biphasic pH dependence on PpIX generation is observed for ALA and its derivatives. Maximal PpIX formation is measured under physiological conditions (pH 7.0-7.6), indicating that further enhancement of intracellular PpIX content may be achieved by adjusting the pharmaceutical formulation of ALA or its derivatives to these pH levels.     

Über die Adsorption potentialbestimmender Ionen

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Neuere Arbeiten über die physikalischen Eigenschaften dünner Metallfilme

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Viscosimetrie

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Nachweis und Bestimmung des Mangans sowie seine Trennung von anderen Elementen

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Laboratoriumsgef?sse

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