Synthesis of Chiral Starburst Dendrimers from PHB‐Derived Triols as Central Cores

Abstract

Chiral triols 1-3 ('tris(hydroxymethy1)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 FrPchet (9 -12, benzyl ethers of 3,5-dihydroxybenzyl alcohol and bromide). In this way, 1st-, 2nd-, and 3rd-generation chiral dendrimers without (1%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 NO, 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 N02-substituted compounds avidly clathrate smaller molecules; they are sorbents exchanging host molecules through the gas phase.

Dendritic TADDOLs: Synthesis, Characterization and Use in the Catalytic Enantioselective Addition of Et2Zn to Benzaldehyde

“…Normally, the (molar) optical rotation value of each chiral building block in a dendrimer is constant, [23,24] and the corresponding contributions of different chiral building blocks can be added up to give the value for the whole molecule. [16,24] Only serious steric hindrance or interaction with other building blocks (e.g.…”

Globular Dendrimers Involving a C60 Core and a Tetraphenyl Porphyrin Function

“…The synthesis of the targets was planned according to the convergent approach developed by Fre  chet and coworkers, [13] taking into account the concept of extended cores developed by Seebach and co-workers. [14,15] With this modification, two new additional steps per generation were added to the Fre  chet route: the O-allylation of benzylic alcohols and the subsequent transformation of the allyl moiety into a terminal alcohol by means of hydroboration. The first-and second-generation dendritic alcohols were obtained according to the synthetic route shown in Scheme 2.…”

C3 Symmetry in Asymmetric Catalysis and Chiral Recognition

“…[170] Although such compounds have been known for several decades, the first syntheses of chiral dendrimers have been undertaken only recently. [171] The chirality of dendrimers may be due either to a chiral nucleus, to which achiral building blocks are attached, or to the attachment of chiral substituents to the core, or, finally, to the use of chiral building blocks, resulting in a chiral interior domain. These kinds of chiral macromolecules are expected to become useful in chemical operations including asymmetric catalysis, chiral recognition, and resolution.…”