Nucleosides antibiotics like

The existence of natural complex nucleoside antibiotics has prompted interest in their syntheses [173]. These compounds are composed of a C5 extended ribonucleoside. This extra chain of two or more carbons carries chiral centers. Some of these nucleosides, like tunicamycins or octosyl acids, can be regarded as C-linked disaccharides and their syntheses are not straightforward. Liposidomycin constitutes another class of complex nucleosides, which has been partially synthesized using a Wittig chain extension at C5 of the furanose derivative 243 [174]. 

Like azole C-nucleosides (Section VI), 1,2-diazole C-nucleosides and their analogs were also extensively studied from both the academic and the applied and medicinal chemistry points of view after the discovery of the naturally occurring C-nucleoside antibiotic pyrazofurin (7). 

In various fungi, including those of Basidiomycotina, numerous nucleoside-type metabolites and related free bases have been found (369). Apart from the typical components that are structural units of nucleic acid chains, like adenosine from Amanita muscaria (9), some of the nucleoside analogs apparently deserve special interest because of their biological and pharmaceutical activities, which eu-e usually induced by a slight difference in structural features. In addition, the role played by such nucleoside antibiotics in protein and nucleic acid biosynthesis might be of great importance. 

Nucleoside antibiotics with a bicyclic carbohydrate unit from Streptomyces cacaoi var. asoensis. Distinctions are made between O. A (pK i 3.0 pKj2 4.3 pKg3 9.4), O. B, and O. C(pK, 3.1 pK 24.5 pK,j 9.9). 0. represent a large group of polyoxin-like antibiotics with antifungal activities. 

Polyoxin D and nikkomycin Z are Streptomyces derived peptidyl nucleoside antibiotics that have been shown to be competitive inhibitors of chitin synthetase in both fungal and insect in vitro systems [39-44]. Both polyoxin D and nikkomycin Z have structural similarities to the substrate UDP-N-acetylglucosamine, which most likely accounts for the competitive nature of their ability to inhibit chitin... 

Members of the PepT family are located on the apical membranes of intestinal and renal epithelial cells and mediate the uptake of several peptidomi-metic drugs like (3-lactam antibiotics, angiotensin-converting enzyme inhibitors, and nucleoside analogs. Currently, two human PepTs have been identified. 

Other important renal transport systems include the peptide transporters, which are involved in the uptake of peptide-like drugs including /3 -lactam antibiotics and angiotensin-converting enzyme inhibitors, and nucleoside transporter proteins, which are involved in uptake of nucleosides and nucleoside analogs (e.g., zidovudine and dideoxyinosine). ... 

Group 5 includes an increasing number of nucleoside-like antibiotics such as puromycin, nucleocidin, and psicofuranine. 

The isolation of a product identical with psicofuranine was simultaneously reported by Yiintsen who had named his product angustmycin C. Structure studies showed that it, too, is 9-D-psicosyladenine. Yiintsen and and Yonehara also isolated another nucleoside-like product which they called angustmycin A and for which they derived structure (31). Hydrolysis of the antibiotic with a strong acid permitted isolation of the adenine, but... 

The sugars from the nucleoside-like antibiotics have been discussed in Section III,5. These are cordycepose (29), D-psicose (30), angustose (33), and amicetose (39). From actinospectacin, the unusual actinospectose (46) was obtained. Hygromycin and hygromycin B have yielded two novel products, 6-deoxy-D-om6mo-hexos-5-ulose (49) and D-talose (51). Novobiocin contains the sugar derivative called noviose (54). 

We have abstracted over 1400 references in carbohydrate chemistry for 1983. The areas of interest reflected in these references have confirmed the trends apparent in recent years. Besides the well-established fields of glycoside, nucleoside, and antibiotic chemistry, there has been a rapid increase in papers reporting the synthesis of chiral natural products from carbohydrate precursors, and a separate chapter on oligosaccharides has clearly justified its inclusion. Incidentally, these last two chapters have both resulted from suggestions made to us by interested readers, and we would like to encourage further participation of this kind. The emphasis in these areas should not obscure the fact that many other aspects of monosaccharide and oligosaccharide chemistry continue to attract much interest, as is demonstrated by the fact that only six of the twenty-four chapters in this volume contain fewer than thirty references. 

---