Models for the Inhibition of Dithiol-Containing Enzymes by Organoarsenic Compounds: Synthetic Routes and the Structure of [PhAs(HlipS2)] (HlipS22− = Reduced Lipoic Acid)
✍ Scribed by Angelika von Döllen; Henry Strasdeit
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 411 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Lipoic acid / S ligands
The arsenic(III) dithiolate [PhAs(HlipS 2 )] (1, HlipS 2Ϫ 2 = re-inhibit enzymes that contain lipoic acid as a cofactor. X-ray structure analysis shows that 1 is a 2,4-disubstituted 1,3,2-duced rac-lipoic acid) has been obtained via three different routes: (A) from (PhAsO) n and rac-dihydrolipoic acid, (B) dithiarsinane, i. e. a six-membered heterocycle. The phenyl group at the 2-position (As) adopts the axial orientation. from (AsPh) 6 and rac-lipoic acid, and (C) from PhAsO(OH) 2 and rac-dihydrolipoic acid. The latter method is also suitable (2RS,4RS)-1, which is the isomer found in the crystal, is thermodynamically more stable than the diastereomeric for the preparation of [(4-NH 2 C 6 H 4 )As(HlipS 2 )] ( ) from (4-NH 2 C 6 H 4 )AsO(OH) 2 . rac-Dihydrolipoic acid and Me 2 -(2SR,4RS)-1 by 4.3 ± 0.8 kJ/mol (25°C). In solution, the epimerization by inversion of configuration at the ψ-tetrahe-AsO(OH) react to give [(Me 2 As) 2 (HlipS 2 )] (3). These reactions indicate pathways by which mono-and diorganoarsenic drally coordinated As atom is faster than expected, with acid catalysis (COOH groups!) being a possible cause. compounds of various As oxidation states (I, III, and V) may [᭛] Part 1: Ref. [1] .