A hemicarcerand composed of two bowls attached at their rims with four O(CH,CH,O), units, when heated with 22 guests containing 6-12 rigidly-arranged non-hydrogen atoms, formed 22 isolable, characterized hemicarceplexes, but failed to form isolable complexes with 34 other potential guests of the same molecular size range.

Hemicarcerand 1, whose synthesis from t w o tetrol bowls and four pentamethylene ditosylate molecules was templated b y veratrole, was found to bind in solution (one-to-one) eighteen different guests; the crystal structure of 104MeCN is centrosymmetric; hemicarcerand 2, containing four hexamethylenedioxy groups, is also discussed.

The unnatural bile pigment analog of bilirubin‐IXα, 2,3,7,13,17,18‐hexamethyl‐(10H,21H,23H,24H)‐bilin‐1,19‐dione‐8,12‐dicarboxylic acid (1), was synthesized as its diethyl ester by coupling 4,4′‐dimethyl‐3,3′‐dicarboethoxydipyrrylmethane‐5,5′‐dialdehyde with 3,4‐dimethylpyrrolin‐2‐one.

A N‐heterocyclic compound containing two hetero atoms, imidazo[5,1‐a]isoindole, was synthesized in 40% yield by the intramolecular photocyclization of N,N'‐bis(o‐chlorobenzyl)imidazolium salts 1 in water (neutral or pH ∼4) or of N‐(o‐chlorobenzyl)imidazole 2, in aqueous acid (pH −4). However, the photocyclized compound 3 was not formed effectively in basic aqueous solution (3 equivalents of sodium hydroxide or pyridine) or in acetonitrile by the photochemical reaction of N,N'‐bis(o‐chlorobenzyl)imidazolium salts 1 or N‐(o‐chlorobenzyl)imidazole (2).

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