Adoc, adamantyloxycarbonyl

Fig. 6. Outline of the synthesis of glucagon by the solution procedure. DCCI, dicyclo-hexylcarbodiimide HOSU, N-hydroxysuccinimide NPS, 2-nitrophenylsulfenyl tBu, t-butyl AdOC, adamantyloxycarbonyl TFA, trifluoroacetic acid...

The reagents for the synthesis of Al -l-adamantyloxycarbonyl amino acid derivatives are similar to those used for other urethane-type protecting groups (Scheme 36). Although the related 1-adamantyl chloroformate (Adoc-Cl, 68) is obtained as crystalline solid, the acylation of amino acids under Schotten-Baumann conditions leads to significant decomposition of the reagent and thus its use does not result in satisfactory yields in all cases. Better results are obtained with 1-adamantyl fluoroformate (Adoc-F, 69) (yields of A -Adoc amino acids 85-95%)P I which is conunerciaUy available or readily prepared from adamantan-l-ol and... 

A further urethane protecting group derived from a secondary alcohol is the 2-ada-mantyloxycarbonyl group.It is more stable toward acidic reaction conditions than the corresponding 1-adamantyloxycarbonyl group (1-Adoc, Section 2.1.2.2.3.3.2), but it is removed with trifluoromethanesulfonic acid or anhydrous HF in a few minutes at... 

However, in the cases examined so far, the molar solubility in DMF has not increased significantly. The 1-adamantyloxycarbonyl (1-Adoc) group could potentially improve the solubility of amino acids and peptides protected by 1-Adoc in organic solvents due to its strong hydrophobicity.P Lys(l-Adoc) was successfully employed in the synthesis of peptide histidine isoleucine (PHI) (Scheme 9)P9 and in the synthesis of a peptide fragment of a lysozyme.P l... 

The m-Boc and S,m-bis-adamantyloxycarbonyl (Adoc) urethane derivatives of Arg have been used for Fmoc SPPS but appear to be inadequate for protection of the guanidino functionality and show substantial ornithine formation [176]. A ft>,a) -bis-Boc derivative has been reported to eliminate ornithine production, although lactam formation is not completely prevented [177]. 

Recent development of single-molecular force spectroscopy by atomic force microscopy (AFM) techniques has enabled quite successfully the measurement of mechanical force produced at a molecular level. Gaub and coworkers reported on a phototriggered polymer, which contains azobenzene units as part of the main polymer backbone (5 Adoc = 1-adamantyloxycarbonyl) (Holland et al., 2003 Hugel et al., 2002). This key study demonstrates a photomechanical cycle using... 

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