Enzymatic alcoholysis of 3′,5′-di-O-acetyl-2′-deoxynucleosides

https://doi.org/10.1016/j.molcatb.2003.11.017Get rights and content

Abstract

Candida antarctica-B (CAL-B) lipase-catalysed alcoholysis of a set of 3′,5′-di-O-acetyl-2′-deoxynucleosides (1ae) gave the corresponding 3′-O-acetyl-2′-deoxy-nucleosides (2ae) in yields ranging from 50 to 96%. The alcohol employed in the biotransformation affected the rate of the enzymatic reaction and the yield of the 3′-O-acetylated product, but in all cases only this regioisomer was formed. The obtained results are in agreement with the regioselectivity displayed by CAL-B lipase in previously reported biotransformations of nucleosides. CAL-B catalysed alcoholysis of 2′,3′,5′-tri-O-acetyl-cytidine and 4-N-acetyl-2′,3′,5′-tri-O-acetylcytidine was also studied, affording with the same regioselectivity the corresponding free 5′-hydroxyl nucleosides.

Introduction

Biotransformations catalysed by hydrolytic enzymes provide convenient methods to achieve regioselective reactions in the sugar moiety of nucleosides. In addition to the usefulness of the described and reviewed enzymatic regioselective acylation and alkoxycarbonylation of nucleosides [1], [2], the hydrolase-catalysed deacylation of nucleosides has also been studied through enzymatic hydrolysis of peracylated deoxynucleosides [3], [4], [5], [6], [7] and ribonucleosides [6], [8], [9].

Over the last years we have been studying the enzymatic deacylation of peracylated ribonucleosides through enzymatic alcoholysis and we have found that Candida antarctica-B (CAL-B) lipase catalyses efficiently the formation of the corresponding 2′,3′-di-O-acylribo-nucleosides [10], [11], [12].

Taking into account these results, we considered of interest to study the behaviour of 3′,5′-di-O-acetyl-2′-deoxynucleosides (1ae, Scheme 1) in the CAL-B catalysed alcoholysis (Scheme 2) and herein we report the results of these biotransformations.

Section snippets

General

Lipase B from Candida antarctica (CAL-B, Novozym 435, 10,000 PLU/mg solid; PLU: propyl laurate units) was a generous gift from Novozymes (Brazil). The enzyme was used straight without any further treatment or purification.

All employed reagents and solvents were of analytical grade and obtained from commercial sources. (2′S)-2′-deoxy-2′-C-methyluridine (1f, Scheme 1) and (2′R)-2′-deoxy-2′-C-methyluridine (1g) were prepared following a previously reported protocol developed by us [13].

Preparation of the substrates 1ai (Scheme 1)

3′,5′-di-O

Results and discussion

Taking into account our previous results on CAL-B catalysed alcoholysis of peracylated ribonucleosides [10], [11], [12], which showed that the best regioselectivity could be reached by carrying out the biotransformations in a very high excess of ethanol, experiments of enzymatic alcoholysis of the diacetylated substrates 1ai were performed using a similar nucleoside/alcohol ratio (see Experimental).

Under these conditions, only one monoacetylated product was formed, giving 3′-O

Conclusions

CAL-B lipase-catalysed alcoholysis of 3′,5′-di-O-acetyl-2′-deoxynucleosides gave the corresponding 3′-O-acetyl-2′-deoxynucleoside in yields ranging from 50 to 96%. In most cases, lower product yields were obtained compared to those afforded by CAL-B lipase-catalysed alcoholysis of peracetylated ribonucleosides [10], [11], [12]. The choice of the alcohol affected the rate of the enzymatic reaction and the yield of the 3′-O-acetylated product, but in all cases only this regioisomer was formed.

Acknowledgements

We thank UNQ, CONICET, SECyT and Fundación Antorchas for partial financial support. AMI and JMM are research members of CONICET. We are grateful to Novozymes (Brazil) for the generous gift of CAL.

References (17)

  • A. Uemura et al.

    Tetrahedron Lett.

    (1989)
  • P. Ciuffreda et al.

    Bioorg. Med. Chem. Lett.

    (1999)
  • P. Ciuffreda et al.

    Tetrahedron

    (2000)
  • H.K. Singh et al.

    Tetrahedron Lett.

    (1993)
  • D.O. Cicero et al.

    Tetrahedron

    (2001)
  • M. Ferrero et al.

    Chem. Rev.

    (2000)
  • D. Kadereit et al.

    Chem. Rev.

    (2001)
  • D.H.G. Crout et al.

    Biocatalysis

    (1990)
There are more references available in the full text version of this article.

Cited by (21)

  • Synthesis of the antitumoral nucleoside capecitabine through a chemo-enzymatic approach

    2015, Tetrahedron Letters
    Citation Excerpt :

    The lithium aluminum hydride reduction of 5′-mesylate 9a,16 which could also remove the 2′ and 3′ acetyl groups, afforded a complex mixture of products. Other attempts, as for example, sodium borohydride in dimethyl sulfoxide17 or sodium cyanoborohydride in hexamethylphosphoric triamide18 did not work since a complex mixture of products was obtained, again. Similar difficulties were encountered using the same reducing agents starting from 5′-bromo derivative 9b, obtained from 8 by reaction with carbon tetrabromide and polymer bound triphenylphosphine,19 in 81% yield.

  • A rational approach to the regioselective deacetylation of 2′,3′,5′-tri-O-acetyluridine by Novozym 435 catalysed alcoholysis

    2012, Biochimica et Biophysica Acta - Proteins and Proteomics
    Citation Excerpt :

    CALB is also one of the most researched enzymes in the field of ester synthesis, glycerolysis and ethanolysis of triglycerides [7]. With nucleosides, CALB shows a regiopreference towards 5′-acylation [4,8,9] and deacylation [10–13]. In the deacylation of ribonucleosides, different reactivities have been obtained in aqueous and non-aqueous media.

View all citing articles on Scopus
View full text