Patent ID: 8846864

Claim:
A compound having the molecular formula I wherein: X is a leaving group or an optionally protected amino acid either alone or as part of a peptide; Y is OH, SH, NH 2 , OR, SR, NHR, or NHRR′ wherein R and R′ are optionally substituted C 1 -C 6 alkyl or acyl, or aryl, or protecting groups; Z is S or SO 2 ; R 1 and R 2 are each independently selected from the group consisting of hydrogen, optionally substituted alkyl, acyl, aryl and halogen; and R 3 , R 4 , R 5 , R 6 , and R 7 are each independently selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted acyl, optionally substituted aryl, nitro and halogen, wherein adjacent groups may together form fused rings; and salts thereof.