Poly(n-butyl isoeyanlde): yellow-brown solid; IR (KBr) 1639 (C=N) cm-1; 'H NMR (CC14) 0.95-1.45 (br, 7 H, (CH2)2CH3), 3.35 (br, 2 H, NCH2).Poly(3-pentyl isocyanide): pale yellow solid; IR (KBr) 1623 (C=N) cm"1.Poly (benzyl isocyanide): brown solid; IR (KBr) 1630 (C=N) cm"1; NMR (CDClt) 4.0-5.0 (br, 2 H, CH2), 6.5-7.S (br, 5 H, ArH). Polv( , -dimethylbenzy 1 isocyanide): pale yellow solid; IR (KBr) 1620 (C=N) cm"1; NMR (CDC13) 2.60 (br, 6 H, CH3), 6.3 (br, 5 H, ArH).Poly(phenyl isocyanide): yellow solid; IR (KBr) 1643 (C=N) cm"1; with the dominant theme being modification of the Koga macrocycle (Figure 1). The most easily transformed region is the "linker", ®, and several workers have varied this unit. Koga varied the length of the linker [( CH2)"] and its rigidity,5b Lehn7 8*and Koga5c introduced chirality by using tartrate-derived linkers, and Vógtle83 built an entirely carbocyclic host with carboxylates as solubilizing units. Diederich first introduced spiropiperidinium units emanating from the diphenylmethane carbon in an effort to remove the charge from the binding region. Later modifications by Diederich included the introduction of further spiropiperidinium units and methyl groups on the aromatic rings.93 Further development continues, and other designs have also received considerable attention.10 Design of a New Class of Hydrophobic Binding Sites. Several years ago we set out to develop a new class of water-soluble molecules with hydrophobic binding sites. Our initial goal, too, was to start with the Koga system-a structure known to bind organic molecules-and modify it in several important ways to enhance binding and the potential utility of the structures for applications in catalysis, transport, etc. The specific improvements we sought were as follows.(9) (a) Diederich, F.;
