| abstract |
The present invention provides a compound having the formula (I) or (II): wherein R1 is selected from halogen and organic moieties; R?2 and R3¿ are independently selected from hydrogen and organic moieties having a mass greater than 15 Daltons where R?2 and R3¿ can together form a carbonyl group or may be joined together within a cyclic structure; Z is an (n+1)-valent atom excluding carbon where n is an integer greater than 0; R4 is independently selected from hydrogen, halogen, and organic moieties having a mass greater than 15 Daltons, with the proviso that at least one R4 (namely R4a) is an organic moiety having a mass greater than 100 Daltons; R5 at each occurrence is independently either halogen or an organic moiety having a mass of less than 500 Daltons; m is selected from 0, 1, 2, 3 and 4; wherein if R2 = R3 = H, then R1 is not CO¿2?(H r CH3) when Z(R4)n is either of -NH(CO)-CH(iBu)-NH(CO)-(CH2Ph or O-t-Bu), and R?4¿ is not CH¿2?CO2t-Bu when Z is OH; and wherein if compounds of both formulae (I) and (II) are present in an admixture, the molar formula (I):formula (II) ratio in the admixture is other than 50:50. The compounds are useful as tags, including tags detectable by mass spectrometry. |