2-cyclopentadienylglycine, a new α-amino acid and its use for η5-complex formation

The reaction of alpha -bromohippuric acid methyl ester with nickelocene, cyclopentadienylthallium or cyclopentadienyltrimethylsilane afforded N-benzoyl-2-cyclopentadienylglycine methyl ester (1) as two double bond isomers 1a and 1b. Similarly, the cyclopentadienyl(Cp)-containing dipeptide Z-L-Phe-DL-(Cp)Gly-OMe (3) was obtained from Z-L-Phe-DL-Gly(Cl)-OMe and trimethylsilylcyclopentadiene. The amino acids 1a, 1b were susceptible to Diels-Alder cycloaddition and yielded dimer 2 as a mixture of regioisomers. Compound 1 and FeCl2 gave 1,1'-fenocenylene-bip(glycine) (5), whereas with [(COD)RhCl](2) rhodium eta (5)-cyclopentadienylglycine (6) and eta (5)-cyclopentadienyldipeptide complexes Like 7 were obtained from 1 or 3, respectively. Unexpectedly, the eta (5)-cyclopentadienylglycine complexes proved to be very sensitive to light. (C) 2001 Elsevier Science Ltd. All rights reserved.