Picolyl groups

The ketiniine 22 derived from benzyl trifluoromethyl ketone and 3-picolylamine. on the other hand, can be prepared.15 Its isomerization to aldimine 23 in triethylamine is complete in 58 hours at room temperature. Thus, the 3-picolyl group is much more reactive than the benzyl group in 14m. but less reactive than the 4-picolyl group. Various bases have been tried in the conversion of 22 into 23.15 Diethylamine is more effective than triethylamine, achieving complete isomerization in 35 hours. In contrast, the reaction catalyzed by DBU is exothermic and complete transformation into 23 can be achieved within a few minutes. 

The calix[6]arene 128 with a syn-arrangement of the a-picolyl groups is < 3v symmetric by its constitution. It forms a copper(I) complex [Cul28X] where the tetrahedral coordination sphere of the copper ion is built up by the three picolyl... 

Although parent compound 47 (s. Scheme 5) and linear reference compounds 49 and (Table 12) which have two picolyl groups showed low extractabilit-ies toward Ag", doubly armed crownophane 48 efficiently extracted Ag", and with excellent selectivity. Ouchi and co-workers reported that a pair of polyether side chains attached at the same carbon atom of a crown ether can interact... 

The isonicotinyloxycarbonyl (iNoc) group has been found to be superior to the benzyloxycarbonyl function usually employed to protect the e-amino-group of lysine. The thiol group of cysteine can be specifically methylated with trimethyl phosphate, whereas twenty other a-amino-acids are completely unaffected by this reagent.The 4-picolyl group can also be used for the 5-protection of cysteine unmasking can be effected by electrolysis. ... 

Scheme 7.10 Methoxyphenyl group, respectively, a-picolyl group as a latent cyclohexenone unit...

The 5-4-picolyl group has been used only rarely in solid-phase synthesis, but it might become useful for the synthesis of large peptides because its presence could confer improved solubility (43, 44). Removal is achieved either by electrolytic reduction or (preferably) by means of Zn-AcOH (44). 

The acetamidomethyl group is recommended for thiol protection in, for example, cysteine it is stable to most peptide coupling conditions, but is readily removed by mercuric ion (Scheme 159). An alternative is the4-picolyl group, which affords protection also to the phenolic group of tyrosine cleavage is achieved by electrolytic reduction. 

Reactions of 4-hydroxy-2-(R-pyridyl)iminothiazolidines 507e-g with the non-substituted 1,2-DAB 155a proceed with the formation of only l-(R-pyridyl) iminosubstituted thiazolo[3,4-a]quinoxalines 508e-g (Scheme 2.118). Thus during the condensation, the aniline and not 2-aminopyridine or 2-aminopicoline is eliminated (Mamedov et al. 2007, 2012). It may be noted that the presence of iminopyridyl and a(Y)picolyl groups in the composition of thiazolo[3,4-a]quinox-alines makes it possible, if necessary, to obtain water-soluble salts of this poly-condensed system. 

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