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Stereochemical relay through oligoureas 24/02/2005.

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Presentation on theme: "Stereochemical relay through oligoureas 24/02/2005."— Presentation transcript:

1 Stereochemical relay through oligoureas 24/02/2005

2 Synthesis Unsymmetrical Symmetrical

3 Alkyl group on meta 6.52 6.47 6.42 6.39 6.36 6.03 5.98 5.90 5.84 5.80 40°C 23°C -10°C -30°C -50°C

4 Alkyl group on meta or ortho position

5 Effect of the chiral sulfoxide The X-ray analysis confirmed that the sulfoxide control the first axis But not the entire helix

6 Effect of the chiral sulfoxide

7 13 C i-Pr sensor The helix exists in two conformations (cis and trans) At 50°C, it seems we can clearly see the two diastereomers.

8 13 C i-Pr sensor 23°C

9 13 C i-Pr sensor 50°C 23°C

10 Benzylic sensor The Br-Li exchange didn’t work. The benzylic position might be the problem

11 Oligoureas connected on the ortho position Broad signals on the 1 H NMR The helix crystallised in a chiral space group as a single enantiomer

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