Big and little Meccano

The syntheses of large-ring compounds

Activation of Protein Phosphatase 1 by a Small Molecule Designed to Bind to the Enzyme's Regulatory Site

We synthesized a series of i- and g-line sensitive non-ionic photoacid generators (PAGs). Photolysis and catalytic properties of the PAGs were examined. Photoreactivity of the PAGs was evaluated using UV-vis spectroscopy. The PAGs were used for photocrosslinking of epoxy-based polymers. The PAGs were also applied to positive-type photoresist materials. Sensitivity profile of the photoresists containing PAGs was affected not only by the photosensitivity of PAGs but also by the acidity of the generated acid. Post-exposure delay of the photoresists was dependent on the molecular size of the generated acid.

Synthesis of i- and g-Line Sensitive Photoacid Generators and Their Application to Photopolymer Systems

Three different types of thiocarboxylic esters (and also thiolactones) exist: the thiol, thioxo- and dithioesters which, according to the IUPAC rules, are named S-alkyl (S-aryl) carbothioates (1), O-alkyl l(O-aryl) carbothioates (2) or alkyl (aryl) carbodithioates (3). Acylation-type reactions were used for the lfirst preparations of thiol carboxylic esters (1) by Tjuttschew (1863),1 Saytzeff and Lukaschewicz l(1868)2 and Michler (1875).3 Thioxocarboxylic esters (2) were first obtained via an acylation route by lMatsui (1908).4 On the other hand, alkyl dithiobenzoates (3; R1 = Ph), which were first mentioned in a lpatent by Bloch and Hohn (1908),5a and alkyl alkanedithioates (3; R1 = Me, Et, PhCH2), first described lby Houben and Schultze (1910),5b were prepared by alkylation of the corresponding metal carbodithioates.

Synthesis of Thioesters and Thiolactones

The trithiosalicylide derivatives (8)–(11) have been synthesised and shown by temperature-dependent 1H n.m.r. spectroscopy to exist in solution as ring inverting (35a)⇌(35b) enantiomeric helical conformations with trans-thioester linkages. The free energies of activation for these conformational changes are ca. 10 kcal mol–1 higher than those for the similar process in the corresponding trisalicylides. In contrast with the trisalicylides, the trithiosalicylides can only ring invert between enantiomeric helical conformations via intermediates containing a cis-thioester linkage. The dithiosalicylide derivatives (3)–(7) have been synthesised; the temperature dependence of the 1H n.m.r. spectrum of di-o-thiothymotide (7) has been interpreted in terms of ring inversion (40a)⇌(40b) between enantiomeric boat conformations. Comparison of the ΔG‡ value of 24.6 kcal mol–1 for this conformational change with that of 17.7 kcal mol–1 previously obtained for di-o-thymotide (41) suggests that cis-thioester linkages are subject to more resonance stabilisation than are cis-ester linkages.

G. Bruce Guise

Papers

Conformational behaviour of medium-sized rings. Part 10. Dithiosalicylides and trithiosalicylides

Dithiosalicylides and trithiosalicylides. Their conformational behaviour in solution