Efficient Synthesis of Nucleoside Diphosphate Glycopyranoses

Abstract

Nucleoside diphosphate pyranoses 1 (NDP sugars; see Scheme 1) play a key role as glycosyl donors in the synthesis of oligo-and polysaccharides. [1,2] Moreover, they serve as precursors of deoxysugars, aminodeoxysugars, chainbranched sugars, uronic acids, as well as glycoconjugates. In biosynthetic pathways the energy-rich linkage between the C1 atom and the b-phosphate is cleaved, and thus the glycosyl part is enzymatically transferred to an oligosaccharide chain, releasing the nucleoside diphosphate (NDP) moiety. For biosynthesis studies of oligosaccharides (for example, of lipopolysaccharides) [3] an efficient access to this important class of compounds is needed. The classical method is the coupling of glycosyl 1-phosphates to nucleotide morpholidates (Moffat-Khorana method). [4,5] However, this reaction normally takes days, and the chemical yields are often low (5-25 %). Attempts to improve the reaction yields by using 1H-tetrazole as activator [6][7][8][9] are often not successful and have failed also in our hands. Instead of the morpholidates, also imidazolides have been used in the past but without improving the yields markedly. [10][11][12] Alternatively, Hindsgaul and Jakeman published a procedure starting from nucleoside diphosphates and glycopyranosyl bromides. [13,14] However, yields were also found to be low, and often the stereochemistry at the anomeric center could neither be controlled nor stereospecifically formed. Thiem and co-workers reported an enzymatic procedure starting from unprotected sugars that were first phosphorylated and then treated with a nucleoside triphosphate. [15,16] However, this reaction sequence is based on a three-enzyme pathway and depends on the availability of the needed kinases and NDP sugar pyrophosphorylases and on expensive nucleoside triphosphates. The yields obtained have seldom exceeded 30 %. Herein, we report on a conceptionally new chemical synthesis of NDP sugars that uses cyclo-saligenyl (cycloSal) nucleosyl phosphate triesters II as an active ester (Scheme 1).Originally, the cycloSal technique was developed to deliver biologically active nucleotides into cells.[17] The cleavage relies on a nucleophilic attack of the neutral phosphate triester by water or hydroxide and a subsequent selective hydrolysis pathway to yield the nucleotide (pathway a-c; Scheme 1). The technique has been applied successfully to a variety of nucleoside analogues, providing superior antiviral activity. [18][19][20] However, the same type of compounds may also be used as an active ester for synthetic applications. Here, cycloSal nucleotides like II were treated with glycopyranosyl 1-phosphate salts III-VI as nucleophiles with formation of the pyrophosphate bond in NDP sugars (pathway d,e; Scheme 1).As starting materials, 5-nitro-cycloSal-3'-O-acetylthymidine 2 and peracetylated glycopyranosyl phosphates 3-6 were prepared (see Scheme 3). Thus, thymidine was protected by silylation with tert-butyldimethylsilylchloride (TBDMS-Cl) at the 5-position. The product was treated with acetic anhyd...

Synthesis of Pyranonucleoside‐6′‐triphosphates through the cycloSal‐Method

“…We first prepared (β-d-glucopyranoside)-thymine (5) and (β-d-galactopyranoside)-thymine (9). This was again achieved by the Vorbrüggen one-pot method.…”

“…Mainly, the Ludwig method is used. [7][8][9][10][11][12][13] With this method the synthesis of nucleoside-5Ј-triphosphates (both natural and non-natural compounds) was accomplished in yields of up to 80 % starting from the cycloSal-compound (64 % starting from the nucleoside). This might explain the low yields that were obtained by this method.…”

“…We have earlier reported on the cycloSal-method for the preparation of phosphorylated bioconjugates. [7][8][9][10][11][12][13] With this method the synthesis of nucleoside-5Ј-triphosphates (both natural and non-natural compounds) was accomplished in yields of up to 80 % starting from the cycloSal-compound (64 % starting from the nucleoside). [8] Herein, the efficient synthesis of pyranonucleoside-6Ј-triphosphates by the cycloSal-method is reported, which was achieved by a new "titration-like" reaction that uses only a slight excess of pyrophosphate, which greatly facilitated purification so that the triphosphates were isolated in good yields.…”

A Modular Synthesis of Modified Phosphoanhydrides

“…Recent notable exceptions to this, however, do exist 4n. q, 22 Nonetheless, the simple, reproducible, and modular coupling under ambient conditions within a few minutes in approximately equimolar amounts of donor and acceptor as described in this publication has been a long‐standing synthetic challenge. The sensitivity of the P‐anhydride forming reaction to a 30‐fold scale‐up has been analyzed in the case of ADP‐βS (0.6 g of starting material 9 instead of 20 mg; see the Supporting Information) and no loss of efficiency regarding yield or purity of ADP‐βS were observed.…”

ChemInform Abstract: How to Form a Phosphate Anhydride Linkage in Nucleotide Derivatives

“…After oxidation of intermediate 10 and hydrolysis of the trimetaphosphate, ATP, CTP,GTP,and UTP of high quality were obtained. [38] Meier et al [39] reported the application of substituted chlorophosphites (11,S cheme 5) for the preparation of cycloSal-nucleotides 12 from appropriately protectedn ucleosides 5. Cyclo-Sal-nucleotides 12 reactedu nder dry conditions with phosphate,p yrophosphate, and various phosphoromonoesters, thereby affording nucleosided i-and triphosphates, dinucleoside 5',5'-di, and tetraphosphates, within 3-5 h. After deprotection and purification, unnatural nucleoside di-and triphosphates 13 wereo btained in 40-80 %y ield (50-62 %y ield for dinucleoside di-or tetraphosphates 13).…”