Treatment of N-protected amino acid active esters, e.g., 3, formed by, the
reaction of N,N-dibenzyl-alanine (2) with DCC and hydroxybenztriazole, with
2 molar equiv of CpLi gives the corresponding amino acid-substituted Cp-an
ion equivalents (e.g., 4). The X-ray crystal structure analysis of 4 has re
vealed a dimeric pentafuluenolate-type structure. Reaction of FeCl2 or (PPh
3)(3)RuCl2 with compound 4 and related reagents yields the respective 1,1'-
difunctionalized metallocenes (7, 8).