A transaminase mimic joining a pyridoxamine unit to a cyclodextrin by a single linkage is quite selective for the conversion of phenylpyruvicacid to phenylalanine, compared with its reactivity toward nonbinding ketoacids. The selectivity is even greater with 4-Zert-butylphenylpyruvic acid but is essentially erased with a phenylpyruvic acid carrying a Zerf-butyl group in the meta position. This strong geometric preferencecan be modified with transaminase mimics in which the pyridoxamine is joined to cyclodextrin bytwo links, greatly restricting the freedom of thesystem. A transaminase has also been prepared with the pyridoxamine unit doubly linked to a synthetic macrocyclic hydrophobic cavity, which has yetother geometric preferences. The doubly linked pyridoxamine units were prepared by use of a novel synthetic procedure for the conversion of olefins to y/c-dithiols. An improved procedure for the preparation of ß-cyclodextrin 6A, 6B diiodide is also described.

Transaminases are a class of enzymes that synthesize amino acids from ketoacids by the simultaneous conversion of pyridoxamine phosphate to pyridoxal phosphate (Scheme I). They are normally selective for particular substrates, and they also show the stereospecificity characteristic of enzymatic processes. We have described a number of mimics of the transaminase enzymes that incorporate pyridoxamine along with other catalytically useful functions. 3, 4