| 摘要 |
A method of forming a thiohydantoin from an N-protected amino acid is described. The method employs a phosphate compound selected from the group consisting of(R1O)(R2O)P(=O)X and(R1O)(R2O)P(=O)-O-P(=O)(OR3)(OR4)to form acylphosphate moieties from the carboxyl groups of internal aspartic acid and glutamic acid residues and an acylphosphate moiety at a C-terminal carboxyl. The later acylphosphate, unlike the internal acylphosphates, spontaneously cyclizes to an oxazolone, which is less reactive with nucleophilic reagents. R1 and R2 are each alkyl, aryl, or alkaryl groups which are the same or different and which may be covalently linked to each other; R3 and R4 are each alkyl, aryl, or alkaryl groups which are the same or different and which may be covalently linked to each other; and X is a leaving group, such as chlorine or bromine, which is substantially unreactive towards thiohydantoins. The acylphosphate and oxazolone moieties are then reacted with a thiocyanate reagent under conditions effective to convert the internal acylphosphates to amides and the terminal oxazolone to thiohydantoin, thereby permitting selective C-terminal thiodantionation of aspartic acid- and/or glutamic acid-containing proteins.
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