3-Methoxalylchromones--versatile reagents for the regioselective synthesis of functionalized 2,4'-dihydroxybenzophenones, potential UV-filters.

The reaction of 1,3-bis-silyl enol ethers with 3-methoxalylchromones affords a great variety of functionalised 2,4'-dihydroxybenzophenones. These products are formed by a domino Michael/retro-Michael/Mukaiyama-aldol reaction. The synthesized compounds are promising candidates for the synthesis of the novel UV-A/B and UV-B filters.

Synthesis of trifluoromethyl-substituted arenes, cyclohexenones and pyran-4-ones by cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 4,4-dimethoxy-1,1,1-trifluorobut-3-en-2-one: influence of the lewis acid on the product distribution.

The TiCl(4)-mediated formal [3 + 3] cyclocondensation of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 4,4-dimethoxy-1,1,1-trifluorobut-3-en-2-one afforded a variety of functionalized 4-methoxy-6-(trifluoromethyl)salicylates and 3-methoxy-5-(trifluoromethyl)phenols with very good regioselectivity. The Me(3)SiOTf-mediated cyclization of 1,3-bis(trimethylsilyloxy)-1,3-butadienes, containing no substituent located at carbon atom C-4 of the diene (R(1) = H), resulted in the formation of trifluoromethyl-substituted pyran-4-ones. In contrast, trifluoromethylated cyclohexenones were formed when dienes were employed which do contain a substituent located at carbon C-4 (R(1) not equal H).

Characterization of a phosphotriesterase-like lactonase from the hyperthermoacidophilic crenarchaeon Vulcanisaeta moutnovskia.

The phosphotriesterase-like lactonase (PLL) encoded by Vmut_2255 in the hyperthermoacidophilic crenarchaeon Vulcanisaeta moutnovskia (VmutPLL), represents the only hyperthermophilic PLL homologue identified so far in addition to the previously characterized thermophilic PLLs from Sulfolobus spp. The Vmut_2255 gene was cloned, heterologously expressed in Escherichia coli; the resultant protein purified and characterized as a 82kDa homodimer (36kDa subunits). The VmutPLL converted lactones and acyl-homoserine lactones (AHLs) with comparable activities. Towards organophosphates (OP) VmutPLL showed a promiscuous but significantly lower activity and only minor activity was observed with carboxylesters. The catalytic activity strictly depended on bivalent cations (Cd(2+)>Ni(2+)>Co(2+)>Mn(2+)>Zn(2+)). Furthermore, VmutPLL showed a pH optimum around 8.0, a temperature optimum of 80°C, and thermostability with a half-life of 26min at 90°C. In this work, the stereoselectivity of a PLL enzyme was investigated for the first time using enantiopure lactones. The VmutPLL showed a slight preference but not an exclusive specificity for the (R)-enantiomers of capro- and valerolactone. The high thermal stability as well as the broad substrate spectrum towards lactones, AHLs and OPs underlines the high biotechnological potential of VmutPLL.