Current Organic Chemistry - Volume 8, Issue 15, 2004

Prebiotic chemistry plays a central role in the investigation of the possible scenarios of the early chemical environments. Its goal is to shed light on the events involved in the synthesis of initial biomolecules and on the selforganization processes that led the last common ancestor. Even though a well defined scenario for the physicochemical conditions on the primitive Earth is not available, one can assume that a synthetic pathway, in order to be considered prebiotic, should use the simplest chemicals and the most common conditions present at that time. Low molecular weight molecules such as hydrogen cyanide and formaldehyde, easily formed from the primitive atmosphere by ultraviolet light, heat or electric discharge as energy sources, have been considered as prebiotic precursors. Here we focus on the attempts to identify the prebiotic events originating purine and pirimidine nucleic acids bases, the necessary components for the assembling of nucleosides, nucleotides and oligonucleotides.

Selected examples of cyclodextrin (CD) oligomers have been presented, describing their syntheses, physicochemical properties and application possibilities. The first part of the review concerns CD dimers, the second one deals with CD trimers and tetramers. The references are cited mainly of reports that appeared during the years 2001-2003.

Although Fischer obtained the first pyridazines as early as 1886, major attention has been devoted to their chemistry only in the early few decades. However, pyridazin-3(2H)-ones and their fused ring derivatives have recently received much more attention to possess various biological activities and also to use new synthetic auxiliaries. The scope of the present review is to summarize from 1990 as the followings; the construction of pyridazin-3(2H)-one ring, the reaction of ring nitrogen (N2), the reaction of ring carbons at C3, C4, C5 and C6 and the application of pyridazin-3(2H)-one derivatives in the synthetic chemistry.

A review focused on different methodologies applied as effective tools for the construction of β phosphapeptides starting from βamino phosphonic and phosphinic acid derivatives as building blocks is reported. βPhosphapeptides can be considered as mimetics of peptides derived from βamino acids, in which the carbon atom of carboxylic acid group is replaced by a phosphorus atom, and these compounds have attracted a particular interest in the preparation of isosteric or bioisosteric analogs of natural products and enzyme inhibitors.

[1,3,5]-Triazine derivatives have traditionally found applications in analytical chemistry as complexation agents, in electrochemistry as multi-step redox systems and as pesticide or herbicide components in agriculture. In the last years, there has been a growing interest in these compounds that have been used, for example, as templates in multidimensional crystal engineering involving metal complexes for producing nanometre sized oligonuclear coordination compounds, as scaffold in combinatorial chemistry and even as new building blocks in peptidomimetics. The continuous demand to develop synthetic methods for the selective preparation of compounds, under mild conditions and by using non-toxic and not expensive reagents, has prompted the researchers to investigate the use of [1,3,5]-triazine derivatives, such as cyanuric chloride and trichloroisocyanuric acid in organic synthetic applications. For this reason cyanuric chloride, and its derived reagents, are used as dehydrating agents in organic synthesis, as coupling agents in the synthesis of peptides, in the preparation of esters, amides, alkyl chlorides, acyl azides, in the selective protection of hydroxyl groups and so on. From this point of view, this reagent appears as a cheap reactive for many group transformations. 1,3,5-Triazine derivatives are versatile reagents even in the oxidation reactions, such as in Swern type process, and in other important oxidation procedures. In this context, another [1,3,5]-triazine derivative such as trichloroisocyanuric acid, which can be conveniently used even in halogenation reactions, can perform efficient oxidations of alcohols. [1,3,5]-Triazine compounds have been employed both as reagents and intermediates in the synthesis of heterocycles and even as “combinatorial core” for the design of new therapeutics.

A review of literature on the synthesis of 8-azasteroids is presented.