草酸盐配体存在于许多类别的材料中,包括储能材料和生物矿物。因此,在原子尺度上确定它们的局部环境对于建立众多相的结构和性质至关重要。在这里,我们证明高分辨率17 O 固态 NMR 对于研究结晶草酸盐系统的结构是宝贵的资产。首先,使用机械化学证明了草酸配体的有效17 O 富集过程。然后, 17 O 富集草酸盐被用于合成生物学相关的一水草酸钙 (COM) 相,从而能够通过高分辨率17 O NMR 分析其结构和热诱导的相变。使用 9.4 至 35.2 T 的磁场以及13 C– 17 O MQ/D-RINEPT 和17 O{ 1 H} MQ/REDOR 实验对低温 COM 形式 (LT-COM) 进行研究,使得待解析草酸盐的8个不等价氧位点,并初步指定。 COM 热处理后的结构变化也通过高分辨率17 O NMR 进行跟踪,为高温形式 (HT-COM) 和无水草酸钙 α 相 (α-COA) 的结构提供
The first regio- and stereospecific synthesis of S-(-)-C-13-malic acid 5 with a high incorporation of C-13 and excellent enantiomeric excess is described. S-(-)-C-13-malic acid 5 was synthesized in a three-step reaction starting with ethyl acetate 2 and diethyl oxalate 1. The produced sodium diethyl oxaloacetate 3 was then enantioselectively reduced with bakers' yeast to S-(-)-C-13-malic acid diethylester 4 which was hydrolyzed to S-(-)-C-13-malic acid 5.
Enantioselective Synthesis of Isotopically Labeled Homocitric Acid Lactone
作者:Jared T. Moore、Nadine V. Hanhan、Maximillian E. Mahoney、Stephen P. Cramer、Jared T. Shaw
DOI:10.1021/ol402802g
日期:2013.11.15
A concise synthesis of homocitric acid lactone was developed to accommodate systematic placement of carbon isotopes (specifically 13C) for detailed studies of this cofactor. This new route uses a chiral allylic alcohol, available in multigram quantities from enzymatic resolution, as a starting material, which transposes asymmetry through an Ireland–Claisen rearrangement.