Efficient chromatographic resolution of a configurationally fragile atropisomeric diphenol via its N-(α)-Boc-tryptophan diesters

Tetrahedron Asymmetry

Volumn 16, Issue 9, 2005, Pages 1681-1684

  Nechab, Malek ^a   Panchal, Bhavesh M ^b   Philouze, Christian ^a   Einhorn, Cathy ^a   Einhorn, Jacques ^a  

^a UNIVERSITÉ JOSEPH FOURIER   (France)

^b Sun Pharma Advanced Research Centre   (India)

Author keywords

[No Author keywords available]

Indexed keywords

4,5 BIS(2 HYDROXYPHENYL)BENZ[F]ISOINDOLE 1,3 DIONE; ISOINDOLE DERIVATIVE; TRYPTOPHAN DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; CHEMICAL STRUCTURE; CHROMATOGRAPHY; CRYSTAL; ENANTIOMER; ISOMERIZATION; PRIORITY JOURNAL; QUANTUM YIELD; SEPARATION TECHNIQUE; STEREOCHEMISTRY; X RAY DIFFRACTION;

EID: 17844407145     PISSN: 09574166     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tetasy.2005.03.011     Document Type: Article

References (13)

1. For a review, see: Y. Ishii, S. Sakaguchi, and T. Iwahama Adv. Synth. Catal. 343 2001 393 427
2. C. Einhorn, J. Einhorn, C. Marcadal, and J.-L. Pierre Chem. Commun. 1997 447 448
3. M. Nechab, C. Einhorn, and J. Einhorn Chem. Commun. 2004 1500 1501
4. C. Einhorn, J. Einhorn, C. Marcadal-Abbadi, and J.-L. Pierre J. Org. Chem. 64 1999 4542 4546
5. Unpublished results
6. C. Einhorn, A. Durif, M.-T. Averbuch, and J. Einhorn Angew. Chem., Int. Ed. 40 2001 1926 1929
7. B.M. Panchal, C. Einhorn, and J. Einhorn Tetrahedron Lett. 43 2002 9245 9248
8. Diesterification has been performed on an analytical scale [10 μmol of (±)-2], with the following commercially available N-protected-l-amino acids: N-Boc-proline, N-Boc-valine, N-Boc-phenylglycine, N-Boc-phenylalanine, N-(α)-Boc-tryptophan, N-(α)-Cbz-tryptophan, and N-(α)-Fmoc- tryptophan. Clearly separated TLC spots were observed only in the phenylalanine, or much better, in the tryptophan series. N-(α)-Cbz and -Fmoc derivatives offer no advantages over -Boc derivatives
9. 2 = 0.1083, 318 parameters. Crystallographic data (excluding structure factors) have been deposited with the Cambridge Crystallographic Data Center as supplementary publication no. CCDC 260846. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge, CB21EZ. UK [fax: +44(0) 1223-336033; e-mail: deposit@ccdc.cam.ac.uk ]
10. For similar observations about the resolution of BINOL derivatives via diastereomeric bis(camphorsulfonates), see: H.-F. Chow, C.-W. Wan, and M.-K. Ng J. Org. Chem. 61 1996 8712 8714
11. As diphenol 2 is prone to thermal isomerisation, special care should be taken to avoid excessive heating during its handling, especially during solvent removal
12. Crystalline solvates formed when amorphous (-)- or (+)-2 was stirred at room temperature for 24 h in a 4:1 mixture of hexane/ethyl acetate. These crystals contained half a molecule of ethyl acetate per molecule of (-)- or (+)-2.
13. 1b,1c,2 at which no racemisation of 2 occurs. Moreover, several catalysts of type 1 bearing bulky R substituents have already been prepared. Preliminary results indicate that they are much more thermally stable than 2. This preliminary study has been conducted with racemic catalysts of type 1, as the absence of cis/trans isomerisation in the racemic series will preclude racemisation (via the cis form) under the same conditions in the optically active series