A spherical cyclic diester has been prepared from the title components, separated from by-products , and purified by aid of double labelling of the components with "H and '&C. respectively. The product may be viewed as a doubly-anchored rotaxane.
Introduction. -We mentioned our intention of using a suitable propellane for the potential threading of its large ring with a bifunctional aliphatic chain, eventually forming an intramolecular rotaxane, 2, (Scheme !). I 2 --SCHEME t We chose to thread a diol of the type I. n=20. The L20.3.3) dione 1 was triated ("H) at the a-positions to the carbonyl groups and reduced to a mixture of the corresponding 24,27diols.z We have found in the interim that conigurational isomers of this type may be distinguished unambiguously. The anti.anti-isomer has a synmatrical NMR spectrua?*' and a strong MH+ peak under isobutane-chemical ionization.' The syn.syn-isomer also has a syraeetrical N?lR spectrum, however, like the syn,anti-isomer, it fragments to give [H-OH]* and [H-OH-H,Ol' under chemical ionization.
The isomer used for threading was the aa-diol (1. anti-anti-OH). We should have expected from a study of models that the aa-diol could perhaps just barely be thresed at all.'-This is based on a concept stemming from the talmud called "Kal vachomer"." If a more difficult action may be accomplished. a simpler analogous one may certainly be done. Thus. although we have not threaded the syn.syn or syn,anti-isomers of the anti,anti-diol we used, if the latter be threaded so must surely the two former isomers as well.