Nucleosides containing Branched-chain Components

5-iV-formylepimine derivative (432) [derived from the diacetal (431)] has been converted into a protected analogue (433) of the polyoxin antibiotics. The stereochemistry of the AT-formylepimine derivative (432) was established by A -ray crystallographic analysis. A series of lipophilic 9-(3-alkyl-3-deoxy-j8-D-ribofuranosyl)adenines (434) has been prepared by glycosylation of 6-benzamido-9-chloromercuripurine with the appropriate branched-chain sugar 

Naturally occurring C-nucleosides and the synthesis of analogous C-nucleosides and functionalized C-glycosides have been reviewed.  

Fox s group has extended its work on the synthesis of pseudocytidine ( -cyti-dine) (Vol. 9, p. 148) to include other 5-D-ribofuranosylpyrimidines. Thus the 3-methoxyacrylate derivative (436) reacted with guanidine, urea, or thiourea to give derivatives of i -cytidine, -uridine, and 2-thio- -uridine and their a-anomers. The D-ribofuranosyl-ethyne and -ethene derivatives (437) and 

Buchanan, A. R. Edgar, M. J. Power, and G. C. Williams, Nucleic Acids Res., Special PubL, 1975, 1 (3rd Symposium Chem. Nucleic Acids Components, 1975), S69 Chem. Abs., 1976, 85, 63 276v). 

Several heterocyclic derivatives have been elaborated from the 6-bromo-6-cyanohex-5-enose (447). For example, the ( )- and (Z)-isomers of (447) reacted with benzylamine to give the cis- and rm j-aziridines (448), respectively, and with guanidine in an alkaline medium to give the diaminopyrimidine derivative 

9-(3-Deoxy-3-C-dichloromethylene-p-D-erythro-pentofuranosyl)adenine has been synthesized from (577), which was obtained straightforwardly from 3-deoxy-3-C- 

Tronchet and D. Schwarzenbach, European J. Medicin. Chem.-Chim. Ther 1976, II, 489 (Chem. Ahs., 1977, 87, 53 512w). 

Alonso, M. T. Garcia-Lopez, G. Garcia-Munoz, and R. Madronero, Anales de 1976, 72, 

Arakawa T. Miyasaka and N. Hamamichi, Nucleic Acids Res Special PubU 1976, 2 (4th Symposium Nucleic Acids Chem., 1976), I (Chem. Abs., 1977, 86, 140 3790. 

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The nucleosides (261) and (371) (analogues of gougerotin) were obtained from branched-chain amino-sugars described in Chapter 15. The assignment of configuration at the branch-point of nucleosides containing a saccharinic acid component is reported in a later section (see p. 156). 

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