This research was financed by grants-in-aid from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (Nos. 15K00408, 24659011, 24640156, 245900425 and 22390005 for Shin Aoki), by a grant from the Tokyo Biochemical Research Foundation, Tokyo, Japan, and by the TUS (Tokyo University of Science) fund for strategic research areas. We would like to thank Noriko Sawabe (Faculty of Pharmaceutical Sciences, Tokyo University of Science) for the measurements of the NMR spectra, Fukiko Hasegawa (Faculty of Pharmaceutical Sciences, Tokyo University of Science) for the measurements of the mass spectra, and Tomoko Matsuo (Research Institute for Science and Technology, Tokyo University of Science) for the measurements of the elemental analyses.

NOTE: All experimental data [NMR, infrared spectroscopies (IR), mass spectroscopies (MS), optical rotations, and elemental analyses data] of the synthesized compounds were reported in a previous paper51.
1. Procedure for O-Glycosylation Reactions
<ol>
	<li>Synthesis of compound &#945;/&#946;-12 (Entry 12 in Table 1) 
	NOTE: Entries 1 - 13 in Table 1 were carried out using a similar procedure.
	<ol>
		<li>Temporar...

The authors have nothing to disclose.

The purpose of this manuscript is to show a convenient synthetic method to prepare disaccharide nucleosides using unprotected ribonucleosides without tedious protecting group manipulations. We report herein on the regioselective O-glycosylations of nucleosides via the temporary 2&#39;,3&#39;-diol protection by a cyclic boronic ester (Figure 1B)51.
The preparation of the cyclic boronic ester intermediate is...

Disaccharide nucleosides, which are conjugates of a nucleoside and a carbohydrate moiety linked via an O-glycosidic bond, constitute a valuable class of naturally-occurring carbohydrate derivatives1,2,3,4,5,6,7. For instance, they are incorporated in biological macromolecules such as tRNA (transfer ribonucleic acid) and poly(ADP-ribose) (ADP = adenosine diphosphate), as well as in some antibacterial agents and other biologically-active substances (e.g., adenophostins, amicetins, ezomycin)5,6,8,9,10,11,12,13,14,15,16,17,18,19. Hence, disaccharide nucleosides and their derivatives are expected to be lead compounds for drug discovery research. The methodologies for the synthesis of disaccharide nucleosides are classified into three categories; enzymatic O-glycosylation20,21, chemical N-glycosylation5,9,16,22,23,24, and chemical O-glycosylation7,9,14,16,18,19,24,25,26,27,28,29,30,31,32,33,34,35,36,37. In particular, chemical O-glycosylation would be an efficient method for the stereoselective synthesis and large-scale synthesis of disaccharide nucleosides. Previous research has shown that the O-glycosylation of 2&#39;-deoxyribonucleoside 2 with the thioglycosyl donor 1, using the combination of p-toluenesulfenyl chloride and silver triflate, affords the desired disaccharide nucleoside 3 (Figure 1A; Ar = aryl and PG = protecting group)38.
Following these results, we decided to develop the O-glycosylation of ribonucleosides applying the p-toluenesulfenyl chloride/silver triflate promoter system. While several examples of the O-glycosylation of partially protected ribonucleosides have been demonstrated7,9,14,16,18,19,24,32,33,34,35,36,37, the use of unprotected or temporarily-protected ribonucleosides as a glycosyl acceptor for O-glycosylation has been negligibly reported. Therefore, the development of regioselective O-glycosylation of unprotected or temporarily-protected ribonucleosides would provide a more beneficial synthetic method without protecting group manipulations of ribonucleosides. In order to achieve the regioselective O-glycosylation of ribonucleosides, we focused on the boron compounds, because several examples of regio- and/or stereoselective acylation, alkylation, silylation, and glycosylation of carbohydrate derivatives assisted by boronic or borinic acid have been reported39,40,41,42,43,44,45,46,47,48,49,50. In this article, we demonstrate the procedure for the synthesis of disaccharide nucleosides utilizing regioselective O-glycosylation at the 5&#39;-hydroxyl group of ribonucleosides via a boronic ester intermediate. In the strategy presented here, boronic ester intermediate 6 would be afforded by the esterification of the ribonucleoside 4 with the boronic acid 5, which allows the regioselective O-glycosylation at the 5&#39;-hydroxyl group with thioglycosyl donor 7 to give the disaccharide nucleoside 8 (Figure 1B)51. We also studied the interaction of a ribonucleoside and boronic acid by nuclear magnetic resonance (NMR) spectroscopy, to observe the formation of a boronic ester. Esterification to make a boronic ester and a glycosylation reaction require anhydrous conditions to prevent the hydrolysis of the boronic ester and the glycosyl donor. In this article, we demonstrate the typical procedures to obtain the anhydrous conditions for successful glycosylation reactions for researchers and students not only in chemistry but also in other research fields.

<table border="0" cellpadding="0" cellspacing="0" style="width:847px;" width="847">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Silver trifluoromethanesulfonate</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">34945-61</td>
			<td style="width:232px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">Phenylboronic acid (contains varying amounts of anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">B0857</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">p-Methoxyphenylboronic acid</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">321-69201</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-(Trifluoromethyl)phenylboronic acid (contains varying amounts of anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">T1788</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">2,4-Difluorophenylboronic acid (contains varying amounts of anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">D3391</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">Cyclopentylboronic acid (contains varying amounts of Anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">C2442</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-Nitrophenylboronic acid (contains varying amounts of anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">N0812</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-Hexylphenylboronic acid (contains varying amounts of anhydride)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">H1489</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Adenosine</td>
			<td style="width:255px;">Merck KGaA</td>
			<td style="width:119px;">862.</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Guanosine</td>
			<td style="width:255px;">Acros Organics</td>
			<td align="right" style="width:119px;">411130050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Cytidine</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">C0522</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Uridine</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">U0020</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">5-Fluorouridine</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">F0636</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">5-Methyluridine</td>
			<td style="width:255px;">Sigma</td>
			<td style="width:119px;">M-9885</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">Methylamine (40% in Methanol,&#160;ca. 9.8mol/L)</td>
			<td style="width:255px;">Tokyo Chemical Industry</td>
			<td style="width:119px;">M1016</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">N,N-dimethyl-4-aminopyridine</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">044-19211</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Acetic anhydride</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">00226-15</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Pyridine, Dehydrated</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">161-18453</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Acetonitrile</td>
			<td style="width:255px;">Kanto Chemical</td>
			<td style="width:119px;">01031-96</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">1,4-Dioxane</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">13622-73</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Dichloromethane</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">130-02457</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Propionitrile</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">164-04756</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Molecular sieves 4A powder</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">04168-65</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Molecular sieves 3A powder</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">04176-55</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Celite 545RVS</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">08034-85</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Acetonitrile-D3 (D,99.8%)</td>
			<td style="width:255px;">Cambridge Isotope Laboratories</td>
			<td style="width:119px;">DLM-21-10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Trifluoroacetic acid</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">34831-25</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:241px;">TLC Silica gel 60 F254</td>
			<td style="width:255px;">Merck KGaA</td>
			<td style="width:119px;">1.05715.0001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Chromatorex</td>
			<td style="width:255px;">Fuji Silysia Chemical</td>
			<td style="width:119px;">FL100D</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Sodium hydrogen carbonate</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">191-01305</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Hydrochloric acid</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">080-01061</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Sodium sulfate</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">31915-96</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Chloroform</td>
			<td style="width:255px;">Kanto Chemical</td>
			<td style="width:119px;">07278-81</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Sodium chloride</td>
			<td style="width:255px;">Wako Pure Chemical Industries</td>
			<td style="width:119px;">194-01677</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Methanol</td>
			<td style="width:255px;">Nacalai Tesque</td>
			<td style="width:119px;">21914-74</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">JEOL Always 300</td>
			<td style="width:255px;">JEOL</td>
			<td style="width:119px;"></td>
			<td>Measurement of NMR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Lamda 400</td>
			<td style="width:255px;">JEOL</td>
			<td style="width:119px;"></td>
			<td>Measurement of NMR</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">PerkinElmer Spectrum 100 FT-IR Spectrometer</td>
			<td style="width:255px;">Perkin Elmer</td>
			<td style="width:119px;"></td>
			<td>Measurement of IR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">JEOL JMS-700</td>
			<td style="width:255px;">JEOL</td>
			<td style="width:119px;"></td>
			<td>Measurement of MS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">PerkinElmer CHN 2400 analyzer</td>
			<td style="width:255px;">Perkin Elmer</td>
			<td style="width:119px;"></td>
			<td>Measurement of elemental analysis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">JASCO P-1030 digital polarimeter</td>
			<td style="width:255px;">JASCO</td>
			<td style="width:119px;"></td>
			<td>Measurement of optical rotation</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">JASCO PU-2089 Plus intelligent HPLC pump</td>
			<td style="width:255px;">JASCO</td>
			<td style="width:119px;"></td>
			<td>For HPLC</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:241px;">Jasco UV-2075 Plus Intelligent UV/Vis Detector</td>
			<td style="width:255px;">JASCO</td>
			<td style="width:119px;"></td>
			<td>For HPLC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Rheodyne Model 7125 Injector</td>
			<td style="width:255px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">58826</td>
			<td>For HPLC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Chromatopac C-R8A</td>
			<td style="width:255px;">Shimadzu</td>
			<td style="width:119px;"></td>
			<td>For HPLC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">Senshu Pak Pegasil ODS</td>
			<td style="width:255px;">Senshu Scientific</td>
			<td style="width:119px;"></td>
			<td>For HPLC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">p-Toluenesulfenyl&#160;chloride</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 38</td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:241px;">Phenyl 6-O-acetyl-2,3,4-tri-O-benzyl-1-thio-a-D-mannopyranoside (a-9)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 52</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-Metylphenyl 2,3,4,6-tetra-O-benzoyl-1-thio-b-D-galactopyranoside (b-21)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 53</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-Metylphenyl 2,3,4,6-tetra-O-benzoyl-1-thio-b-D-glucopyranoside (b-31)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 57</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:241px;">4-Metylphenyl 2,3,4,6-tetra-O-benzoyl-1-thio-a-D-Mannopyranoside (a-32)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 67</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">6-N-Benzoyladenosine (14)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 54</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">2-N-Isobutyrylguanosine (16)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 55</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:241px;">4-N-Benzoylcytidine (20)</td>
			<td style="width:255px;"></td>
			<td style="width:119px;"></td>
			<td>Prepared&#160; Ref. 56</td>
		</tr>
	</tbody>
</table>

regioselective o-glycosylation of nucleosides via the temporary 2',3'-diol protection by a boronic ester for the synthesis of disaccharide nucleosides

Disaccharide nucleosides, which consist of disaccharide and nucleobase moieties, have been known as a valuable group of natural products having multifarious bioactivities. Although chemical O-glycosylation is a commonly beneficial strategy to synthesize disaccharide nucleosides, the preparation of substrates such as glycosyl donors and acceptors requires&#160;tedious protecting&#160;group manipulations and a purification at each synthetic step. Meanwhile, several research groups have reported that boronic and borinic esters serve as a protecting or activating group of carbohydrate derivatives to achieve the regio- and/or stereoselective acylation, alkylation, silylation, and glycosylation. In this article, we demonstrate the procedure for the regioselective O-glycosylation of unprotected ribonucleosides utilizing boronic acid. The esterification of 2&#39;,3&#39;-diol of ribonucleosides with boronic acid makes the temporary protection of diol, and, following O-glycosylation with a glycosyl donor in the presence of p-toluenesulfenyl chloride and silver triflate, permits the regioselective reaction of the 5&#39;-hydroxyl group to afford the disaccharide nucleosides. This method could be applied to various nucleosides, such as guanosine, adenosine, cytidine, uridine, 5-metyluridine, and 5-fluorouridine. This article and the accompanying video represent&#160;useful (visual) information for the O-glycosylation of unprotected nucleosides and their analogs for the synthesis of not only disaccharide nucleosides, but also a variety of biologically relevant derivatives.

The results of the O-glycosylation of uridine 10 with thiomannoside &#945;-9 are summarized in Table 160,61. In Entry 1, the O-glycosylation of 10 with &#945;-9 in the absence of boronic acid derivatives resulted in the formation of a complicated mixture. In Entry 2, 10 and phenylboronic acid 11a...

Watch this Scientific Journal Video about Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides at JoVE

Regioselective O-Glycosylation of Nucleosides via the Temporary 2&#039;,3&#039;-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

Here, we present protocols for the synthesis of disaccharide nucleosides by the regioselective O-glycosylation of ribonucleosides via a temporary protection of their 2&#39;,3&#39;-diol moieties utilizing a cyclic boronic ester. This method applies to several unprotected nucleosides such as adenosine, guanosine, cytidine, uridine, 5-methyluridine, and 5-fluorouridine to give corresponding disaccharide nucleosides.

Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides

Disaccharide nucleosides, which consist of disaccharide and nucleobase moieties, have been known as a valuable group of natural products having ...

This method can be expected to help drug discovery research because of short process needed for the preparation of biologically-active disaccharide nucleosides as compared with traditional existing methods. The main advantage of this technique is that unprotected nucleosides can be applied for glycosylation without a tedious protecting group manipulation to synthesize disaccharide nucleosides. Visual demonstration of this method will present useful information for successful glycosylation of unprotected nucleosides for researchers and students, not only in chemistry but also in other research fields.To begin, optimize the reaction conditions for the synthesis of compound Alpha-and Beta-12 as described in the text protocol. Next, apply the optimized reaction conditions to the synthesis of Beta-22 to Beta-30, as well as for Beta-33, using a similar procedure. In this video, the synthesis of compound Beta-22 is demonstrated.Begin with the temporary protection of two prime, three prime-Diol of ribonucleoside by dissolving 20.4 milligrams of Adenosine-13 in 0.76 milliliters of anhydrous pyridine in a 10 milliliter pear-shaped flask. Then, add 80.4 milligrams of galactosyl donor Beta-21. Now add 21.7 milligrams of four-Trifluoromethyl phenylboronic acid 11C.This boronic acid alternative is used because it gave Alpha-and Beta-12 in the highest chemical yield during optimization. Evaporate the mixture, dissolved in 0.76 milliliters of anhydrous pyridine, using the rotary evaporator. Then, co-evaporate the resulting reaction mixture with 0.76 milliliters of anhydrous pyridine twice, followed by 0.76 milliliters of anhydrous one four-dioxane three times at room temperature to approximately 40 degrees Celsius to remove any water.Dissolve the residue in 0.76 milliliters of anhydrous one four-dioxane and stir the reaction mixture at its reflux temperature for one hour to form a boronic ester as a temporary protection. Remove the solvent using a rotary evaporator, followed by a vacuum pump. Meanwhile, in a 10 milliliter two-neck round-bottom flask with a septum attached to it, add 150 milligrams of four-angstrom molecular sieves powder.Heat the molecular sieves in a microwave under atmospheric pressure. Then, cool them under reduced pressure, evacuated by a vacuum pump three times. After cooling, dry the sieves with a heat gun under reduced pressure, while replacing the air with argon gas several times.To perform the glycosylation, dissolve the residue resulting from vacuum decompression in 1.50 milliliters of anhydrous propionitrile and transfer this solution to a flask containing the molecular sieves. Stir the reaction mixture at room temperature for 0.5 hours, followed by cooling it to minus 40 degrees Celsius. Now, add 117.6 milligrams of silver triflate followed by 30.3 microliters of para toluenesulfonyl chloride to the reaction mixture at the same temperature.Stir the reaction mixture at minus 40 degrees Celsius for 1.5 hours. Next, check the reaction by thin-layer chromatography with two to one hexane diethyl acetate to check the glycosyl donors and with 10 to one chloroform to methanol to check the glycosyl acceptors and products. Quench the reaction mixture with 2.0 milliliters of saturated aqueous sodium bicarbonate.Then, dilute the reaction with 3.0 milliliters of chloroform. Now, remove the insoluble materials through celite and carefully wash the celite with 30 milliliters chloroform. Using a 100 milliliter separatory funnel, wash the filtrate with 30 milliliters of saturated aqueous sodium bicarbonate three times.Then, wash the filtrate with 30 milliliters of brine. Dry the resulting organic layer with sodium sulfate. After filtering the insoluble materials, concentrate the filtrate using a rotary evaporator.Purify the remaining residue by silica gel column chromatography with a chloroform methanol gradient ranging from a one to zero ratio to a 30 to one ratio to afford the Beta-22. Continue synthesis of other compounds as detailed in the text protocol. In a 10 milliliter pear-shaped flask, dissolve 34.3 milligram of Uridine 10 in one milliliter of anhydrous pyridine.Add 40.0 milligrams of four trifluoromethyl phenylboronic acid 11C. Co-evaporate the reaction mixture with one milliliter of anhydrous pyridine three times and then one milliliter of anhydrous one four dioxane three times at room temperature to approximately 40 degrees Celsius to remove any water. Dissolve the residue in anhydrous 1.40 milliliters of one four dioxane.Then, stir the reaction mixture at its reflux temperature for one hour to form a boronic ester as a temporary protection. Now, dispense the 0.14 milliliters of the reaction mixture to a five milliliter vial. Remove the solvent from the five milliliter vial using a rotary evaporator, followed by a vacuum pump.Dissolve the resulting residue in 0.64 milliliters of tridutero acetonitrile. Finally, measure proton, boron 11 and fluorine 19 NMR spectrum using a quartz NMR tube at 25 degrees Celsius. Reaction conditions for the glycosylation of Uridine 10 with glycosyl donor Alpha-nine were optimized.The condition, as shown in entry 12, gave the disaccharide nucleoside Alpha-and Beta-12 in highest chemical yield. Shown here are the results of the glycosylations of various nucleosides 10 and 13 through 20 with glycosyl donor Beta-21, that when used with optimized reaction conditions, afford the corresponding disaccharide nucleosides Beta-22 through Beta-30 in the highest yields. While attempting this procedure, it's very important to obtain the anhydrous conditions using sufficient redried flask, molecular sieves and solvents to avoid the hydrolysis of boronic ester on the glycosyl donor.The application of the temporary protection of hydroxyl groups by boronic ester will be useful for the synthesis of a variety of natural and artificial compounds, as well as disaccharide nucleosides.

regioselective-o-glycosylation-nucleosides-via-temporary-2-3-diol

Research

JoVE Journal

Chemistry

8.6K visualizações.  Tokyo University of Science. This method can be expected to help drug discovery research because of short process needed for the preparation of biologically-active disaccharide nucleosides as compared with traditional existing methods. The main advantage of this technique is that unprotected nucleosides can be applied for glycosylation without a tedious protecting group manipulation to synthesize disaccharide nucleosides. Visual demonstration of this method will present useful information for successful glycosylation of ...

Vídeo: Regioselective O-Glycosylation of Nucleosides via the Temporary 2',3'-Diol Protection by a Boronic Ester for the Synthesis of Disaccharide Nucleosides