1- Adamantyl fluoroformate

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... 

Adamantyl fluoroformate was prepared with a yield of 91% by acylating 1-adamantanol with COCIF [1436]. Adamantylisopropanol, (16.5), when treated in dichloromethane or diethyl ether with COCIF in the presence of triethylamine, gave (16.6) in a yield of greater than 90% [1063,1070,2120]. 

The adamantyl carbonate is prepared from Adoc2C03 (DMAP, CH3CN, >79% yield) or, in the case of electron-deficient phenols, the fluoroformate (THF, Pyr, 54-95% yield). It is somewhat more stable to TFA than the adamantyl carbamate. 

Peptide synthesis, N-protection Acetic-formic anhydride. Adamantyl chloroformate. Benzylthiocarbonyl chloride. /-Butoxycarbonyl-N-hydroxysuccinimide ester. /-Butyl azido-formate. /-Butylcarbonic diethylphosphoric anhydride. /-Butyl fluoroformate. /-Butyl oxycarbonyl fluoride. /-Butyl pentachlorophenyl carbonate. /-Butyl 2,4,5-trichlorophenyl carbonate. Carbobenzoxy chloride. 3,5-Dimethoxybenzyl p-nitrophenyl carbonate. [2-(Diphenyl)isopropyljphenyl carbonate. /-Pentyl chloroformate. 

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