N-Hydroxysuccinimidyl chloroformate

A modification of Zalipsky s method by Miron and Wilchek (1993) simplifies the creation of the SC-activated species. Instead of using highly toxic phosgene to form a chloroformate intermediate and then reacting with NHS, the new procedure utilizes either N-hydroxysuccinimidyl chloroformate or N,N -disuccinimidyl carbonate (DSC Chapter 4, Section 1.7) to produce the SC-PEG in one step (Figure 25.6). Since both activation reagents are commercially available, creating an amine-reactive PEG derivative has never been easier. 

Figure 25.6 An alternative route to an SC derivative of mPEG can be accomplished by the reaction of the terminal hydroxyl group of the polymer with either N,N -disuccinimidyl carbonate or N-hydroxysuccinimidyl chloroformate.

Since BAs occurring in food do not exhibit satisfactory absorbance or fluorescence in the visible or ultraviolet range, chemical derivatization, either pre- (35-37) or postcolumn (38), is usually used for their detection in HPLC. The most frequently employed reagents for precolumn derivatization are fluorescamine, aminoquinolyl-lV-hydroxysuccinimidyl carbamate (AQC) (39, 40), 9-fluorenylmethyl chloroformate (FMOC) (41-43), 4-dimethylaminoazobenzene-4 -sul-fonyl chloride (dabsylchloride, DBS) (44), N-acetylcysteine (NAC) (45,46), and 5-dimethyl-amino-1-naphthalene-1-sulfonyl chloride (dansylchloride, DNS) (47,48), phthalaldehyde (PA), and orf/to-phthaldialdehyde (OPA) (49-51), together with thiols such as 3-mercaptopropionic acid (MPA) (37) and 2-mercaptoethanol (ME) (35,49). 

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