Current Organic Synthesis - Volume 3, Issue 1, 2006

Encapsulation of [60]fullerene by cyclic molecules like cyclodextrins and calixarenes has many different applications. One of the earliest among them was to enhance the solubility of [60]fullerene in both polar as well as non-polar solvents and this has had immense application potential in materials research and medicine. Molecular modeling studies are efficient tools to study the supramolecular structures and have the advantage of predicting the structures even before carrying out an experiment. Unlike the naturally occurring cyclodextrins that cannot be easily obtained by a totally synthetic procedure, calixarenes are the product of the condensation reactions between para-substituted phenols and formaldehyde. These bowl-shaped molecules have cavities that can hold metals as well as molecules and have been used to sequester metal ions. This review highlights the research done in the nanoencapsulation of fullerenes by cyclodextrins and calixarenes during the last decade and looks at the emerging trends in this area.

There is a large requirement in modern molecular biology for the production of specifically conjugated oligonucleotides. For instance, oligonucleotides may be conjugated to fluorescent labels to allow sequence specific detection following a biological assay. A number of methods exist for the conjugation of oligonucleotides and mainly rely on the use of a nucleophile attached to the oligonucleotide reacting with reactive species to form the desired product. A new approach to achieve oligonucleotide conjugations is to use cycloadditions. This review covers the growing use of cycloadditions for labelling of oligonucleotides at various positions within the sequence and the advantages over existing techniques. A number of different dienes have been reported and each is reviewed. Finally, the use of these conjugated oligonucleotides is reported with a view, to demonstrate the advantages of using cycloaddition for the conjugations.

The series of oligopyridine ligands has increasingly become one of the most popular ligands in coordination chemistry. While the lower members of this series, 2,2'-bipyridine (bpy) and 2,2':6',2''- terpyridine (tpy), are mostly used due to their easy synthetic accessibility and predictable coordination behaviour, the higher members have also attracted chemists' interest. The higher the number of pyridine ring is, the lower is the solubility. Though some aromatic rests were attached to pyridine rings to increase the solubility. In addition, the higher oligopyridines may react, depending on metal ions, in different manners, e.g. they can be divided into subunits. This may be a drawback, however, this property was used to prepare fascinating metal complexes. These two properties make them as attractive and challenging synthetic molecules for chemists and material scientists. In this paper the synthetic strategies used to prepare the higher oligopyridine ligands are reviewed comprehensively.

A small, but extraordinary diverse class of bioactive styryl-lactones has been isolated from several species of the genus Goniothalamus (Annonnaceae). The interesting biological properties, in particular antitumoral, and structural diversity of these lactones have prompted several asymmetric syntheses. They may be classified in two types: synthesis from enantiomerically pure material (carbohydrate...) or with asymmetric methodologies (dihydroxylation, epoxidation...). This review will discuss the different strategies implemented to prepare these styryl-lactones.

Catalysts and cyanide sources for asymmetric synthesis of cyanohydrins are reviewed with 175 references.

Morphine (1) and its O-methylated analogue codeine (2), analgesic alkaloids of the opium poppy (Papaver Somniferium), have been targets of organic chemists engaged in synthetic activities for at least half a century. The "first" (Gates) and "most efficient" (Rice) syntheses of morphine (1) and codeine (2) are well known and have been reviewed and analyzed extensively numerous times. However, syntheses of the same two alkaloids that have been reported since 1992 and which have been used as devices to advance the art of organic synthesis are not as widely recognized and they have not been as thoroughly reviewed. Here they are analyzed in the spirit of the use of these two compounds as templates. Further, since both racemic and enantiospecific syntheses are important and since all eight (8) approaches (since 1992) are sufficiently different so as to warrant more tha n superficial examination, they are all considered.