SYNTHESIS OF CHIRAL STARBURST DENDRIMERS FROM PHB-DERIVED TRIOLS AS CENTRAL CORES

Chiral triols 1-3('tris(hydroxymelhyl)methane' derivatives), prepared from (R)-3-hydroxybutanoic acid and aldehydes, are used as center pieces of dendrimers. The triols may be employed as such or after attachment of spacers containing alkyl or aryl moieties (see 5 and 7). The branches combined with the original or elongated triols are those first reported by Frechet (9-12, benzyl ethers of 3,5-dihydroxybenzyl alcohol and bromide). In this way, 1st-, 2nd-, and 3rd-generation chiral dendrimers without (13-15), or with aliphatic (16-18) or aromatic (19-21) spacers are prepared. The molecular weights range from 447 to 2716 Dalton. Two of the chiral triols, i.e., 2 and 3, are used as center pieces for chiral dendrimers containing 6 NH2, or 6 and 12 NO2 groups on the periphery (22-27), with 3,5-dinitrobenzoyl chloride as the branching unit. All compounds thus synthesized are of course monodisperse and are fully characterized. In some cases, the optical activity of the dendrimers indicates that conformationally chiral substructures might be present. The NH2 and NO2-substituted compounds avidly clathrate smaller molecules; they are sorbents exchanging host molecules through the gas phase.