Synthesis 2010(10): 1573-1589  
DOI: 10.1055/s-0029-1218757
REVIEW
© Georg Thieme Verlag Stuttgart ˙ New York

Michael-type Addition as a Convenient Method for Regioselective N-Alkylation of Ambident Uracils

Sławomir Boncel, Andrzej Gondela, Krzysztof Walczak*
Department of Organic Chemistry, Biochemistry and Biotechnology, Silesian University of Technology, Krzywoustego 4, 44-100 Gliwice, Poland
Fax: +48(32)2372094; e-Mail: Krzysztof.Walczak@polsl.pl;
Further Information

Publication History

Received 8 January 2010
Publication Date:
28 April 2010 (online)

Abstract

A review of the Michael-type addition as one of the convenient synthetic methods to N-functionalisation of the uracil ring - against the background of other typical alkylation methods - is presented. The topic of N1- versus N3-regioselectivity in alkylation reactions is emphasised since this differentiation is essential in the various, especially medicinal, applications of substituted uracils. Specifically, the addition of uracils to acrylic acceptors at the N1-position is frequently used in the first stage of the synthesis of pyrimidinic acyclic nucleosides. In turn, the N3-position of the uracil ring is useful in further transformations, like anchoring of biologically active fragments in conjugates for radiochemotherapy or carriage of covalently bonded drug molecules. Nevertheless, N3-substituted derivatives of pyrimidine nucleosides can, themselves, play various therapeutic roles. Fundamental theoretical premises are also detailed, with regard to the rationale behind the orientation of alkylation.

1 Uracils in Medicine

2 Reactivity of the Uracil Ring

2.1 Electronic Structure and Tautomerism

2.2 Uracil Derivatives as N-H Acids

3 Alkylation of Uracils

3.1 Alkylation of Uracils in the Formation of N-Glycosidic Bonds

3.2 Synthesis of Acyclic Nucleosides

3.3 Alkylation of Uracils with Selected Electrophiles

3.4 N1- and N3-Alkylation of Uracils via Michael-type Addition­

3.5 Synthesis of Michael-type Uracil N3 Adduct Analogues

4 Conclusions and Perspectives

89

Crystallographic data for this compound were deposited in The Cambridge Crystallographic Data Centre under reference number CCDC-656160.

90

Crystallographic data for this compound were deposited in The Cambridge Crystallographic Data Centre under reference number CCDC-728270.