Tomáš Pospíšil

2,5-dimethylphenacyl esters: a photoremovable protecting group for phosphates and sulfonic acids.

2,5-Dimethylphenacyl phosphoric and sulfonic esters release the corresponding acids upon irradiation in nearly quantitative isolated yields, with quantum yields phi = 0.71 and 0.68 in methanol, 0.09 and 0.19 in benzene. In methanol solution the reactions proceed predominantly via the (Z)-photoenol, the lifetimes of which (20 and 25 micros) were determined by laser flash photolysis. The chromophore is proposed as an excellent photoremovable protecting group for use in organic synthesis and biochemistry.

Photoenolization-Induced Oxirane Ring Opening in 2,5-Dimethylbenzoyl Oxiranes To Form Pharmaceutically Promising Indanone Derivatives

Irradiation of 2,5-dimethylbenzoyl oxiranes results in a relatively efficient and high-yielding formation of β-hydroxy functionalized indanones that structurally resemble biologically active pterosines. Nanosecond laser flash photolysis and quantum-chemical calculations based on density functional theory provided evidence that this photochemical transformation proceeds primarily via a photoenolization mechanism. Our study revealed considerable complexity of the mechanism and that structural modifications can significantly alter the reaction pathway and yield different products. The scope of this photochemical transformation for the synthesis of some pharmaceutically important compounds was investigated.

Photochemical synthesis of substituted indan-1-ones related to donepezil

A photoenolization reaction is shown to be the key reaction step in the preparation of substituted indan-1-ones as convenient precursors for the synthesis of donepezil, a well-known acetylcholinesterase inhibitor. Model 2,5-dialkylphenacyl chlorides, differently substituted in the alpha-carbon position, were found to produce indan-1-ones upon irradiation in non-nucleophilic solvents in high chemical yields via hydrogen chloride release. While direct excitation of 4,5-dimethoxy-2-methylphenacyl chloride led to a complex mixture of photoproducts, photolysis of the corresponding benzoate was found to form 5,6-dimethoxyindan-1-one in 62-72% chemical yields and a relatively low quantum efficiency (Phi approximately 0.02). This compound can then be easily converted to donepezil by standard synthetic steps described in the literature. Isotopic exchange and quenching experiments revealed that the product is obtained by the photoenolization process via the triplet excited state, while minor side-photoproducts originate from the singlet excited state. Irradiation of the reactant in neat acetone, used both as a triplet sensitizer and solvent at the same time, was found to form 5,6-dimethoxyindan-1-one exclusively in high (90%) chemical yield.

The Bomb, the Cold War and the Czech Film

This article addresses the theme of nuclear disaster in Czech cinema of the second half of the 20th century. Examining two films based on Karel ˇapek’s cautionary novel Krakatit (Krakatit, 1947; Temné slunce [Dark Sun], 1980) and the 1966 feature Konec srpna v hotelu ozón [The End of August at Hotel Ozone], it demonstrates the impact of the changing political situation on the Czech film industry and the resulting film productions. These case studies allow the author to demonstrate the close interconnectedness between the films’ texts and their respective discursive fields, as well as the impact of fear of nuclear apocalypse in the population at large.

The five senses of Canadian cinema: introduction

This introduction attempts to briefly situate the volume within the relevant theoretical context and present the individual authors and their papers. While highlighting some of the main points the contributors make, it also identifies various thematic and methodological overlaps running through the volume, which are of particular relevance to Canadian cinema and culture.

As crippled as it gets : Dalton Trumbo's Johnny Got His Gun (1939; 1971)

The paper offers a contrastive analysis of Dalton Trumbos novel Johnny Got His Gun (1939) and its film adaptation (1971) and situates them in their respective personal and social contexts.