1. A simple convenient synthesis of L-[4-13C]glutamine
Kokoro Nagasawa, Atsushi Kishida, Masahiro Kajiwara, Tomoyuki Kanamatsu, Kazuhiko Takatori J Labelled Comp Radiopharm. 2015 Feb;58(2):42-5. doi: 10.1002/jlcr.3265.
L-[4-(13)C]Glutamine was synthesized from sodium [2-(13)C]acetate in 12 steps and 18% overall yield. A Wittig reaction of (R)-benzyl 4-formyl-2,2-dimethyloxazolidine-3-carboxylate and ethyl 2-(triphenylphosphoranylidene)[2-(13)C]acetate prepared from D-serine and sodium [2-(13)C]acetate, respectively, gave (4S)-4-(2-ethoxycarbonyl[2-(13)C]vinyl)-2,2-dimethyloxazolidine-3-carboxylic acid α,β-isopropylidene group, oxidation of the resulting hydroxyl group to a carboxyl group and transamidation of the ester moiety gave L-N-Cbz-[4-(13)C]glutamine (Cbz = benzyloxycarbonyl). Finally, removal of the Cbz group gave L-[4-(13)C]glutamine. L-[4-(13)C]Glutamine can be prepared in fewer steps and higher yield by this method compared with previously reported methods.
2. Glycosylation with N-Troc-protected glycosyl donors
U Ellervik, G Magnusson Carbohydr Res. 1996 Jan 11;280(2):251-60. doi: 10.1016/0008-6215(95)00318-5.
N-Troc-protected (Troc = 2,2,2-trichloroethoxycarbonyl) glucosamine and galactosamine glycosyl donors (1-O-acetyl sugar, bromo sugar, and thioglycoside) were compared with the corresponding N-Phth-protected derivatives in glycosylations of 2-(trimethylsilyl)ethanol, 2-bromoethanol, methyl 3-mercaptopropionate, N-Fmoc-protected serine, and 2-(trimethylsilyl)ethyl 6-O-benzyl-2-deoxy-2-phthalimido-beta-D-glucopyranoside. The N-Troc-protected donors gave pure beta-glycosides in somewhat higher yields than the N-Phth-protected counterparts. The N-Troc protecting group can be removed by reduction with zinc, which allows selective N-deprotection in oligosaccharides containing both N-Troc and N-Phth groups.
3. Pentynyl dextran as a support matrix for immobilization of serine protease subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic media
Muhammad Nazir Tahir, Eunae Cho, Petra Mischnick, Jae Yung Lee, Jae-Hyuk Yu, Seunho Jung Bioprocess Biosyst Eng. 2014 Apr;37(4):687-95. doi: 10.1007/s00449-013-1038-8. Epub 2013 Aug 25.
In this study, serine protease (subtilisin Carlsberg) was immobilized on pentynyl dextran (PyD, O-alkynyl ether of dextran, 1) and used for the transesterification of N-acetyl-L-phenylalanine ethyl ester (2) with different aliphatic (1-propanol, 1-butanol, 1-pentanol, 1-hexanol) and aromatic (benzyl alcohol, 2-phenyl ethanol, 4-phenyl-1-butanol) alcohols in tetrahydrofuran (THF). The effect of carbon chain length in aliphatic and aromatic alcohols on initial and average transesterification rate, transesterification activity of immobilized enzyme and yield of the reaction under selected reaction conditions was investigated. The transesterification reactivity of the enzyme and yield of the reaction increased as the chain length of the alcohols decreased. Furthermore, almost no change in yield was observed when the immobilized enzyme was repeatedly used for selected alcohols over six cycles. Intrinsic fluorescence analysis showed that the catalytic activity of the immobilized enzyme in THF was maintained due to retention of the tertiary structure of the enzyme after immobilization on PyD (1).
