ORGN 776 |
| We describe a new synthesis for the backbone-rigidified folding aromatic oligoamides that have been developed in our laboratory. The direct synthesis of these folding aromatic oligomers was found to become increasingly inefficient as chain length extends, which, most likely, is due to the steric hinderance introduced by the folded (helical) conformation of the corresponding oligomers. Thus, by using the 2,4-dimethoxybenzyl (DMB) group to temporarily remove some of the backbone amide hydrogens, the backbone-rigidifying three-center hydrogen bonding is interrupted, which in turn disrupts the folded conformation. It was found that the reactivity of the building blocks carrying the N-DMB groups increased nearly 40 times as compared to the ones without the DMB group. The DMB groups can be conveniently removed using trifluoroacetic acid (TFA), which releases the amide hydrogen in the last step, leading to oligomers that fold back into helical conformations. Using this novel strategy, a series of oligoamides (up to 15mer) were obtained in good yields. Complexation of L-arginine methyl ester by the corresponding folding oligomers led to strong Cotton effects in the corresponding CD spectra, which confirmed the adoption of helical conformations.
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Total Synthesis, Materials, Molecular Recognition, Process R&D, and Physical Organic Chemistry
8:00 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster
Division of Organic Chemistry |
