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Updated: May 4, 2026

Synthesis and Bioconjugation of Thiol-Reactive Reagents for the Creation of Site-Selectively Modified Immunoconjugates
Published on: March 6, 2019
An important side reaction using the thiol, 3,6-dioxa-1,8-octanedithiol (DODT), in 9-fluorenylmethoxycarbonyl-based
Paul W R Harris1, Renata Kowalczyk, Sung-Hyun Yang
1School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland, 1142, New Zealand; Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
Abstract:
A considerable quantity of an alkylation by-product is observed when using 3,6-dioxa-1,8-octanedithiol as a scavenger during acidic release of peptides containing the thioether amino acid methionine from the solid support. Adjustment of the cleavage conditions by replacement of 3,6-dioxa-1,8-octanedithiol with ethane dithiol or by using methionine sulfoxide as an alternative to methionine resulted in no such impurity. The by-product was detectable by liquid chromatography and mass spectrometry and characterised by NMR spectroscopy of an isolated model peptide. It could be effectively removed in a separate post cleavage step by treatment with dilute aqueous acid at 37 °C.
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