This review targets new trends in nucleoside biotechnology which have emerged during the last decade. anticancer and antiviral drugs; ( iii ) a need for further study of known and novel enzymatic transformations and their use as tools for the efficient synthesis of new nucloside analogs and derivates with biomedical potential. This article will review all of these aspects and also include a brief retrospect Deforolimus of this field of research. inos – muscle) was Deforolimus isolated from beef extract by J.F. von Liebig in 1847. He referred to its taste intensifier property also; synthesis of IMP from inosine and its own framework as ribofuranoside 5’-monophosphate was referred to by P.A. Levene & R.S. Tipson 88 years later on (Structure 1) [1]. It really is interesting to notice that Deforolimus it had been P.A. Levene who coined the overall Deforolimus term “nucleotide” for phosphoric acidity derivatives shaped as the consequence of nucleic acidity hydrolysis and recommended the word “nucleoside” for dephosphorylated nucleotides and also identified D -ribose and later 2 D -ribose as Deforolimus constituents of RNA and DNA respectively [2 – 7]. Pioneering structural studies on nucleosides and nucleotides during the last decade of the 19 and first decade of the 20th centuries showed that DNA and RNA consist of five heterocyclic bases and two pentoses. The first chemical condensation of these two of two components was reported by E. Fischer & B. Helferich in 1914 [8]; condensation of a silver salt of 2 8 with 2 3 4 5 O -acetyl- α – D -glucopyranosyl bromide followed by deprotection and hydrodehalogenation yielded a nonnatural nucleoside N 9 -( β – D -glucopyranosyl)adenine ( 10 ) whose structure was unequivocally proved by J.M. Gulland & L.F. Story 24 years later (Scheme 1) [9]. Between World War I and II a number of very important studies dedicated to the chemical synthesis of pyrimidine and purine nucleosides were published but systematic studies on the chemical synthesis of nucleosides nucleotides and oligomers were started by A. MGP Todd and his co-workers in 1942 at Cambridge University in England and somewhat later in the USA. Since then numerous books and reviews have been published on the subject summarizing the enormous progress achieved (see [10 – 12]). Systematic studies of the biological properties of nucleosides began in the second half of the 1940 Somewhat earlier P. Fildes & D.D. Woods formulated the antimetabolite theory and a resulting approach to the design of natural compound analogs with biomedical potential sparked an enormous amount of research in this area (for the relevant reviews see [13 14 Despite the moderate predictive power of this theory synthesis of a large variety of natural nucleoside analogs and data on their biological properties yielded ( i ) very useful tools for studying biochemical transformations which facilitated understanding of the mechanism of functioning of enzymes of nucleic acids metabolism; ( ii ) an analysis of the structure-activity relationships which allowed rational design of new analogs with improved activity-toxicity ratios; and ( iii ) a number of anticancer and antiviral drugs. Deforolimus Thirty years of systematic studies resulted in the discovery of several major structures of great biological and medicinal importance such as heterocyclic bases (6-mercaptopurine (11) thioguanine (12) 5 (13) ) analogues of thymidine modified at C5 of an aglycone (2 ′ -deoxy-5-iodouridine (14) Idoxuridine ; Iduviran; 2 ′ -deoxy-5-fluorouridine (15) FUDR Floxuridine; ( E )-5-(2-bromovinyl)-2 ′ -deoxyuridine (16) BVDU Brivudine) and at C3 ′ of the carbohydrate moiety (3 ′ -deoxy-3 ′ -fluorothymidine (17) FLT Alovudine and 3 ′ -deoxy-3 ′ -azidothymidine (18) AZT Zidovudine) β -D-arabinofuranosyl nucleosides (1-( β – D -arabinofuranosyl)-cytosine (19) aC Cytarabine; -adenine (20) aA Vidarabine; -guanine (21) aG) 3 β – D metabolic activation and deactivation. Moreover these studies identified the enzymatic reactions involved in these activities and also led to the discovery of the role of nucleoside utilization mechanisms (“salvage” synthesis) and the participation of virus-encoded nucleoside kinases in an integral stage of nucleoside activation via intracellular 5 ′ -monophosphorylation..