Spontaneous substitution of azulene-derived benzylic alcohols by thiols and its application to labeling/protection of biothiols

By mixing guaiazulene-3-methanol derivatives and thiols at room temperature, benzylic substitution of the alcohol proceeded to yield the corresponding sulfide. Because of the blue color of the guaiazulene derivative, this spontaneous reaction was used for labeling of paper-immobilized biothiols. By treatment with tris(2-carboxyethyl)phosphine hydrochloride, the guaiazulene-3-ylmethyl part of the sulfide could be removed and the original thiol recovered. Based on these findings, a guaiazulene-3-methanol derivative was used as a protective group for the synthesis of cysteine derivatives. To create your abstract, type over the instructions in the template box below. Fonts or abstract dimensions should not be changed or altered. [Display omitted] •Guaiazulene-3-methanol derivatives undergo spontaneous benzylic substitution with thiols.•Due to blue color of azulenes, the above reaction could be applied to the naked eye detection of immobilized biothiols.•The guaiazulene-3-ylmethyl group on the sulfides can be removed by treating with TCEP to regenerate the thiols.•The guaiazulene-3-methanol derivatives could be utilized as protective groups for Cys-containing peptides.