Current Organic Chemistry - Volume 14, Issue 6, 2010

Carbohydrates are complex and structurally diverse compounds in nature with key roles in a broad range of life processes, including signal transduction, carcinogenesis and immune responses. Many natural products contain oligosaccharides that are vital for their biological activity. However, the synthesis of complex oligosaccharides and other glycoconjugates is hampered by difficulties associated with the regioselective protection of polyhydroxyls and challenges related to the stereoselective assembly of glycosidic linkages. Therefore, a big challenge in glycochemistry is to have selectively protected monosaccharide units, one with a strategically positioned free hydroxy group (a nucleophilic acceptor for further glycosylation or functional-group modifications) and suitable protecting groups on the remaining hydroxyls. The present review discusses some of the most recent advances in the synthesis of these building blocks by regioselective protection or deprotection procedures. These strategies have permitted to achieve hundreds of different building blocks, with a good potential in a combinatorial approach synthesis of complex glycoconjugates. Special focus will be positioned on the new advances in biocatalysis in these reactions.

Synthesis of racemic polyhydroxylated carbobicyclic derivatives having a decalin or hydrindane structure is reviewed. The emphasis is put on the mechanistic aspects of the formation of such derivatives using various approaches. Biological activity of these compounds is discussed.

This review reports on the synthetic strategies developed for chiral N,P; N,S; and N,O pyridine ligands in the last decade. Asymmetric reactions catalyzed by metal complexes of these ligands will be discussed.

Single enantiomers of functionalised benzopyran-3-amines are widely used in the pharmaceutical industry as building blocks or intermediates in the synthesis of drugs acting as 5-hydroxytryptamine and dopamine receptor ligands, as well as inhibitors of dopamine β-monooxygenase. Several approaches for the preparation of the key benzopyran-3-amine intermediates in optically pure form are discussed, including synthesis and resolution of racemic mixtures, application of starting materials from the chiral pool, asymmetric synthesis and chromatographic techniques. Several examples of some larger scale production processes are provided, together with a discussion of the advantages and limitations of each approach.

Synthesis of optically pure polyhydroxylated, carbobicyclic derivatives with the decalin or hydrindane structure is described. The emphasis is put on the application of the useful chirons derived from the chiral pool. This paper presents the methodology which is complementary to the one reviewed in the previous chapter describing the synthesis of the racemic derivatives.