G-Alkylation derivatives

Basic carriers (Table 27.1) consist mainly of amine-based compounds such as quaternary ammonium salts (e.g., Aliquat 336), tertiary amines (e.g., tri-n-octylamine [TOA], tri-isooctylamine [TlOA]), weakly basic compounds (e.g., alkyl derivatives of pyridine N oxides), and thiadiazine derivatives (e.g., 5-(4-phenoxyphenyl)-6/f-l,3,4-thiadiazin-2-amine [FFAT]). The reason for this classification is related to the similarity in the extraction mechanism involving the carriers discussed. In the case of fully substituted quaternary ammonium compounds (e.g., Aliquat 336), the carrier reacts as an anion exchanger forming an ion-pair with another anion from the feed phase, which can be a complex metal anion. In the case of amine and other weak bases mentioned earlier, the carrier must be protonated first in order to allow anion exchange with another anion from the feed phase or with a complex metal anion. Alternatively, the carrier may react directly with a protonated complex metal anion [16]. 

N-Glucuronides of 5-fluorouracil and its 2-G-alkyl derivatives (N -glycosylated) have been reported, 2.163 and N -benzyladenosinc-5 -uronamides and their 2-substituted derivatives have been synthesized as As-selective adenosine agonists. 

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