... Tetrahedron: Asymmetry. Volume 14, Issue 5, 7 March 2003, Pages 619–627. ... 14 The dark brown color was also observed when 10 mg ml −1 (1.3 mmol ml −1 ) of the resin was used instead of the normal 5 mg ml −1 , but in this case the enzymatic acylation was also prevented. ...