Expeditious procedure to synthesize ethers and esters of tri- and tetrahydroxy[6]helicenebisquinones from the dye-intermediates disodium 4-hydroxy- and 4,5-dihydroxynaphthalene-2,7-disulfonates

A procedure is described for synthesizing appreciable quantities of both th e tetradodecyloxy[6]-helicenebisquinone 1 (R = dodecyl), which exhibits uni que optical properties but previously was difficult to prepare, and a varie ty of analogues. The synthesis starts from disodium 4,5rlihvdroxynaphthalen e-2, 7-disulfonate, the commercially available dye-interme diate known as c hromotropic acid. It gives enantiopure 1, with R = (i-Pr)(3)Si, whose silyl groups can be replaced by dodecyl and hexanoyl groups. The same procedure applied to disodium 4-hydroxynaphthalene-2,7disulfonate, also an inexpensiv e, commercially available chemical, works equally well to produce the corre sponding molecules that have one fewer side chain. Key steps are the use of tosyl groups to protect phenols and of a method described seven years ago by Satoh, Itoh, Miura, and Nomura to transform the sulfonic acid functions to iodides. The structure of tetra-(1S)-camphanate 20, the ester of the red uction product of (-)-1 [R = (i-Pr)(3)Si], was analyzed by X-ray diffractio n. It shows the absolute configurations and supports the presumed basis for the rule that the (1S)-camphanates of(P)-helicen-1-ols are more polar than their (M)-diastereomers.