Transition metal ('Fischer-type') carbene complexes as protein labelling reagents

The electrophilic property of metallocarbenes of Fischer-type was used to l abel amino acid derivatives and a model protein in a regio-specific manner with a transition heavy metal complex. Hence, the reaction of (CO)(5)W=C(OM e)Me (1) was shown to involve exclusively the amino group of a series of al pha -amino esters whether this function was carried by the alpha -carbon or by the side chain, leading to stable aminocarbenes. With a model protein, namely bovine serum albumin, labelling also occurred involving solely the a mine function of some of its lysine residues. Coupling yield was shown to d epend both on the pH where the reaction was carried out, and on the quantit y of carbene. This work could find an application in the field of protein X -ray crystallography. (C) 2001 Elsevier Science B.V. All rights reserved.