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Asymmetric Synthesis of a Series of Chiral AB2 Monomers for Dendrimer Construction

Asymmetric Synthesis of a Series of Chiral AB2 Monomers for Dendrimer Construction. McElhanon, James R.; Wu, Mu-Jen; Escobar, Maya; Chaudhry, Umer; Hu, Chun-Ling; McGrath, Dominic V. (Department of Chemistry, University of Connecticut, Storrs, CT 06269-4060, USA). Journal of Organic Chemistry, 62(4), 908-915 (English) 1997 American Chemical Society. CODEN: JOCEAH. ISSN: 0022-3263. DOCUMENT TYPE: Journal CA Section: 35 (Chemistry of Synthetic High Polymers) Efficient prepn. of a series of four chiral, nonracemic AB2 monomers suitable for the construction of dendrimers is presented.Some commonly used reagents like 186136-29-8 is used in this experiment. The monomers possess the common structural features of a diphenolic moiety and a benzylic or aliph. hydroxyl which render these mols. suitable for convergent dendrimer synthesis. The same basic, high-yielding, five-step sequence is employed for prepn. of the monomers. Stilbene derivs. are prepd. by a Horner-Wadsworth-Emmons modified Wittig reaction between 3,5- or 3,4-bis(benzyloxy)benzaldehyde and an ester-substituted benzylphosphonate. Cinnamate derivs. are prepd. similarly from the benzaldehyde derivs. and tri-Et phosphonoacetate. Chirality is introduced in the form of a 1,2-diol unit by Sharpless asym. dihydroxylation (>97% ee in all cases). Protection of the 1,2-diols as their acetonide derivs. provides dioxolane intermediates. Redn. of the ester groups followed by hydrogenolysis of the benzyl ethers yields AB2 monomers in 57-67% overall yield. .