1.Synthesis of 3-Deoxy-L-ketohexoses through Group Transfer.
Lu TN1, Chang CC1. J Org Chem. 2016 Jan 15;81(2):469-75. doi: 10.1021/acs.joc.5b02257. Epub 2015 Dec 30.
A practical method for the synthesis of 3-deoxy-L-ketohexoses is described. Both D- and L-ketohexoses can be transformed into rare 3-deoxy-L-ketohexoses in six steps through a group transfer process. The key step involves a radical cyclized onto a carbonyl group, followed by a fragmentation reaction, eventually resulting in the group transfer of an α-oxy carbonyl group. The process involves tin-free and environmentally benign radical conditions (TTMSS/AIBN/toluene). The acyclic form of 3-deoxy-L-fructose was prepared in only three steps from the inexpensive starting material, D-fructose. A further modification by preparing a dithioacetal derivative was accomplished, which could serve as a convenient sugar synthon for further synthetic applications. Removal of the dithioacetal protecting group results in the formation of the rare 3-deoxy-L-fructose in a total yield of 42%. This methodology could be further extended to the synthesis of other deoxy-L-ketohesoses, such as 3-deoxy-L-sorbose.
2.AuPt Alloy on TiO2: A Selective and Durable Catalyst for L-Sorbose Oxidation to 2-Keto-Gulonic Acid.
Chan-Thaw CE1, Chinchilla LE2, Campisi S1, Botton GA2, Prati L1, Dimitratos N3, Villa A4. ChemSusChem. 2015 Dec 21;8(24):4189-94. doi: 10.1002/cssc.201501202. Epub 2015 Nov 27.
Pt nanoparticles were prepared by a sol immobilization route, deposited on supports with different acid/base properties (MgO, activated carbon, TiO2 , Al2O3, H-Mordenite), and tested in the selective oxidation of sorbose to 2-keto-gulonic acid (2-KGUA), an important precursor for vitamin C. In general, as the basicity of the support increased, a higher catalytic activity occurred. However, in most cases, a strong deactivation was observed. The best selectivity to 2-KGUA was observed with acidic supports (TiO2 and H-Mordenite) that were able to minimize the formation of C1/C2 products. We also demonstrated that, by alloying Pt to Au, it is possible to enhance significantly the selectivity of Pt-based catalysts. Moreover, the AuPt catalyst, unlike monometallic Pt, showed good stability in recycling because of the prevention of metal leaching during the reaction.
3.Enzymatic synthesis of rare sugars with L-rhamnulose-1-phosphate aldolase from Thermotoga maritima MSB8.
Li Z1, Wu X2, Cai L3, Duan S4, Liu J4, Yuan P4, Nakanishi H5, Gao XD6. Bioorg Med Chem Lett. 2015 Sep 15;25(18):3980-3. doi: 10.1016/j.bmcl.2015.07.027. Epub 2015 Jul 17.
L-Rhamnulose-1-phosphate aldolase from a thermophilic source (Thermotoga maritima MSB8) (RhaDT.mari) was heterologously overexpressed in Escherichia coli and the stereoselectivity of this enzyme with or without Nus tag was investigated. We also applied this enzyme to the synthesis of rare sugars D-psicose, D-sorbose, L-tagatose and L-fructose using our one-pot four-enzyme system. To the best of our knowledge, this is the first use of RhaD from a thermophilic source for rare sugar synthesis and the temperature tolerance of this enzyme paves the path for large scale fermentation.