Biological Activity and Other Uses

This review deals with methods for the synthesis of 1,2,4-triazine mono-lV-oxides and their reactivity. The interest in 1,2,4-tiiazines is due to their incorporation in many natural and artificial compounds, their biological activity, and other useful properties. 

Preparation of thiadiazoles via the Hurd-Mori cyclization has led to the synthesis of a variety of biologically active and functionally useful compounds. Discussion of reactions prior to 1998 on the preparation of thiadiazoles have been compiled in a review by Stanetty et al Recent syntheses of thiadiazoles as intermediates for useful transformations to other heterocycles have appeared. For example, the thiadiazole intermediate 36 was prepared from the hydrazone 35 and converted to benzofuran upon treatment with base. Similarly, the thiadiazole acid chloride 38 was converted to the hydrazine 39 which, upon base treatment, provided the pyrazolone, which can be sequentially alkylated in situ to provide the product 40. ... 

A number of 4-pyrimidinecarboxylic acids of the general formula (XVI) and their esters, amides and nitriles are claimed to possess cardiovascular, hypotensive, and spasmolytic properties [214]. Other biological activities and medicinal uses of 5-halo-substituted orotic acids, as well as those of uracil-6-sulphonic acid and related compounds, have been discussed in Part I of this review [215]. 

Considering that only a small fraction of the 20000 Asteraceae species as the major pool of STL structures have been subject to phytochemical studies, and that many plants of other families may contain such compounds, the knowledge on their structural diversity as described in the first section will increase further in the future. At the same time, their biological activity and potential use is a field of very active research in many groups and it appears that a lot of interesting findings in this respect are yet to be made. 

Cinchona alkaloids comprising quinine, quinidine, cinchonidine, and cinchonine as the major members constitute a unique class of quinoline alkaloids with tremendous impact on human civilization. The odyssey of Cinchona alkaloids began with the discovery of their antimalarial properties followed by the very successful application in stereochemistry and in asymmetric synthesis. Currently, the portfolio of applications of Cinchona alkaloids is much broader, involving chiral stationary phases for enantioselective chromatography, novel biological activities, and several useful transformation converting them into other modular and chiral building blocks, such as, for example, quincorine or quincoridine. Current pressure on a more intense exploration of sustainable products and easy access to diverse molecular architectures make Cinchona alkaloids of primary importance for synthetic catalytic and medicinal chemistry. 

Litvinov, V. P. Heteryladamantanes reeent synthetie investigations, biological activity and other aspects of practical use (review). Chemistry of Heterocyclic Compounds, 2002 vol. 38, >fo 1, 9-34. Translated from Khimiya Geterotsiklieheskikh Soedinenii, 2002 >fo. 1, 12-39. 

The field of pyridopyridazines, although potentially a rich one, has been little explored compared with that of the pyridopyrimidines. This is due partly to the difficulty of preparation of several of the member systems, to the relatively small number of different syntheses utilized for those systems which have been explored, and the relative lack of interesting biological activity, or pharmaceutical and other uses found with them. 

The hypocrellins (7-9) are Class B perylenequinones that have also been the subject of much investigation due to their biological activity, having been used in Chinese folk medicine for the treatment of vitiligo, psoriasis, and other diseases for... 

A representative series of enantiomerically pure alkaloids and other compounds having known biological activity was synthesized using the above described strategy by the group of Prof. Denmark (Chart 3.19). 

Additional data on the use of oxazine (539) and products of its modifications in syntheses of compounds having potential biological activity and their precursors are presented in Scheme 3.274 (541). Catalytic hydrogenation of the imino and oximino fragments is primarily used for this purpose. This approach made it possible to prepare a representative series of nitrogen-containing heterocycles and of other previously unknown compounds. 

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