In the presence of Candida antarctica lipase B, the alcoholytic ring opening of 5‐substituted oxazinones proceeds as kinetic resolution (KR) and affords N‐acyl β2‐amino acid esters in up to 96 % ee, the remaining oxazinones were obtained in up to 99 % ee. In the presence of triethylamine as racemization catalyst, the enzyme‐catalyzed alcoholytic oxazinone opening proceeds as dynamic kinetic resolution (DKR), affording quantitative yields of N‐protected β2‐amino acid esters in high enantiomeric purity (up to 96 % ee). N,C‐double deprotection to afford the β2‐amino acid can be effected without loss of enantiopurity.
Colourless single crystals of the caffeine adduct of mercurous perchlorate dihydrate, [Hg2(Caf)2](ClO4)2(H2O)2, were grown from aqueous solutions of mercurous perchlorate and caffeine by isothermal evaporation at ambient temperature. The crystal structure (monoclinic, P21/n, Z = 4, a = 1628.0(2), b = 780.4(1), c = 2229.6(3) pm, β = 99.84(1)°, R1(all data) = 0.0894) contains [trans‐Caf‐Hg‐Hg‐Caf]2+ cations with a Hg‐Hg distance of 250.88(6) pm, Hg‐N (bond) distances of 214.4(6) and 215.1(6) pm and Hg‐Hg‐N angles of 176.9(2) and 165.1(2)°, respectively. These cations are attached via weak Hg‐O contacts to dimers which are further arranged to leave large channels into which one crystal water molecule is included. The second water molecule and the two perchlorate anions are weakly attracted to one Hg atom.
Enantiopure β 2 -Amino Acids. -In the presence of triethylamine as racemization catalyst, the enzyme-catalyzed alcoholic oxazinone opening proceeds as dynamic kinetic resolution, affording N-protected β-amino acid esters in high enantiomeric purity. Double deprotection can be effected without loss of enantiopurity. -(BERKESSEL*, A.; JURKIEWICZ, I.; MOHAN, R.; ChemCatChem 3 (2011) 2, 319-330, http://dx.
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