- Stereoselective N-glycosylation with N4-acyl cytosines and efficient synthesis of gemcitabine
-
Through systematical comparison of various N4-protected cytosine derivatives in the glycosylation step of gemcitabine synthesis, highly beta-stereoselective and high yielding TBAI catalyzed N-glycosylation was achieved with N4-Bz cytosine and anomeric mixture of 2,2‘-difluororibose mesylate donor. The subsequent global deprotection gave gemcitabine efficiently. Meanwhile, the anomeric chloride intermediate and fluoride-displaced side products of this N-glycosylation were identified, too. This new glycosylation method reveals the importance of N4-protection in the stereoselective preparation of pyrimidine nucleoside, also provides a potential alternative to current industrial process to gemcitabine.
- Liu, Tongchao,Tang, Jiadeng,Liang, Jianpeng,Chen, Yabin,Wang, Xiaowen,Shen, Jingkang,Zhao, Dongmei,Xiong, Bing,Cen, Jun-Da,Chen, Yue-Lei
-
p. 1203 - 1213
(2019/01/29)
-
- Inactivation of lactobacillus leichmannii ribonucleotide reductase by 2',2'-difluoro2'-deoxycytidine s'-triphosphate: Covalent modification
-
Ribonucleotide reductase (RNR) from Lactobacillus leichmannii, a 76 kDa monomer using adenosylcobalamin (AdoCbl) as a cofactor, catalyzes the conversion of nucleoside triphosphates to deoxynucleotides and is rapidly ( 3H]- and [5-3H]F2CTP were synthesized and used independently to inactivate RNR. Sephadex G-50 chromatography of the inactivation mixture revealed that 0.47 equiv of a sugar was covalently bound to RNR and that 0.71 equiv of cytosine was released. Alternatively, analysis of the inactivated RNR by SDS-PAGE without boiling resulted in 33% of RNR migrating as a 110 kDa protein. Inactivation of RNR with a mixture of [1'-3H]F2CTP and [1'-2H]F 2CTP followed by reduction with NaBH4, alkylation with iodoacetamide, trypsin digestion, and HPLC separation of the resulting peptides allowed isolation and identification by MALDI-TOF mass spectrometry (MS) of a 3H/2H-labeled peptide containing C731 and C736 from the C-terminus of RNR accounting for 10% of the labeled protein. The MS analysis also revealed that the two cysteines were cross-linked to a furanone species derived from the sugar of F2CTP. Incubation of [1-3H]F2CTP with C119S-RNR resulted in 0.3 equiv of sugar being covalently bound to the protein, and incubation with NaBH4 subsequent to inactivation resulted in trapping of 2'-fluoro-2'-deoxycytidine. These studies and the ones in the preceding paper (DOI: 10.1021/bi9021318) allow proposal of a mechanism of inactivation of RNR by F2CTP involving multiple reaction pathways. The proposed mechanisms share many common features with F2CDP inactivation of the class I RNRs.
- Lohman, Gregory J.S.,Stubbe, Joanne
-
body text
p. 1404 - 1417
(2011/02/21)
-