Cj. Easton et al., N,N '-bis(6(A)-deoxy-beta-cyclodextrin-6(A)-yl)urea as a molecular template in the formation of indigoid dyes, NEW J CHEM, 22(11), 1998, pp. 1163-1165
The title cyclodextrin dimer biases competing reactions of indoxyl anion to
give indirubin and indigo against the latter, due to the preferred geometr
y of alignment of the cyclodextrin annuli.