Current Organic Chemistry - Volume 11, Issue 9, 2007

Nitrile ylides are of considerable interest both from a theoretical and a synthetic viewpoint. Both aspects are discussed in the first account contributed by Prof. S. Vazquez and his co-workers from the University of Barcelona, Spain. Hydrazonates can be converted to a wide variety of heterocycles as demonstrated by Prof. Shawali and Prof. Sherif from the University of Cairo, Egypt. Unnatural α-amino acids is an active field where heterocyclic molecules are of considerable importance both during the synthetic build-up and as targets. The recent advances in the field have now been reviewed by Drs A. Perdih and M. Sollner form the University of Ljubljana, Slovenia. Butylphthalides constitutes natural products and synthetic analogues with diverse biological effects. The progress in the area has now been scrutinized by Dr Li and Dr Xiong from the Sichuan College of Education, China.

The preparation, physical and spectroscopic properties, and applications to organic synthesis of nitrile ylides are reviewed.

The chemistry of esters of hydrazonoic acids has gained increased interest in both synthetic organic chemistry and biological fields. Since a large number of developments in the use of such esters, a review of such developments, covering the literature up to mid 2005, seems to be of considerable value. The present review presents their structural features, nomenclature, synthetic methods and chemical reactions. The utility of the latter reactions for synthesis of various heterocyclic ring systems including mono-, bi-, tri-, tetra-, and penta-heterocycles. In addition, their silicon chelates and biological applications are presented.

The synthesis of unnatural α-amino acids is an area of research that has gained a lot of attention in recent years. The availability of synthetic methods for novel unnatural αamino acid derivatives and related compounds will be a critical point in the de novo design of molecules that mimic the conformation of the natural, active peptides. These molecules (peptidomimetics) are designed to display high receptor affinity and selectivity, in addition to enhanced bioavailability and metabolic stability. This review focuses on selected recent synthetic methodologies leading to unnatural α-amino acids including chiral catalysts that enable enantioselective synthesis and microwave-assisted synthesis. Solid phase synthesis and construction of organometallic αamino acids reveal the scope of influence that this field has in organic chemistry. Additionally, the article is aimed to provide a brief insight into the biosynthetic approaches to the synthesis of α-amino acid derivatives, and to give the reader an appreciation of the field.

3-n-Butylphthalide (1) and its analogues, which are the main components in the volatile oil of celery as well as a wide range of umbelliferae and composite plants, have potential applications as hypotensive drugs because of their strong pharmacological activities, such as improving the microcirculatory system of man's brain, improving nervous function deficiency, antiasthma, anticonvulsion, inhibiting platelet aggregation, inhibiting prostaglandin (PG) F2a growth, enhancing blood flow volume, antitumorigenesis, hypotensive activity and so on, so the investigation on the syntheses and applications of them has attracted considerable attention. The significant synthetic methods of 3-n-butylphthalide and its analogues were summarized and discussed in this review and it is expected that it may be valuable for their further development and applications.