Stereoselective acylation of 20-(S)-camptothecin with amino acid derivatives using scandium triflate/DMAP

Tetrahedron Asymmetry

Volumn 9, Issue 6, 1998, Pages 915-918

  Greenwald, Richard B ^a   Pendri, Annapurna ^a   Zhao, Hong ^a  

^a Enzon Incorporated   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

4 AMINOPYRIDINE DERIVATIVE; AMINO ACID DERIVATIVE; CAMPTOTHECIN DERIVATIVE; CARBOXYLIC ACID DERIVATIVE; CYANAMIDE; SCANDIUM;

ACYLATION; ARTICLE; CHEMICAL REACTION; CHIRALITY; DRUG PURITY; ESTERIFICATION; ISOMER; PRIORITY JOURNAL; RACEMIC MIXTURE; STEREOCHEMISTRY;

EID: 0032571506     PISSN: 09574166     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0957-4166(98)00056-1     Document Type: Article

References (8)

1. Greenwald, R. B.; Pendri, A.; Conover, C. D.; Lee, C.; Choe, Y. H.; Gilbert, C.; Martinez, A.; Xia, J.; Wu, D.; Hsue, M. Bioorganic and Medicinal Chemistry 1998 (in press).
2. Under similar conditions, the preparation of the less hindered t-butyl ester, t-butyl-L-Cbz-Ala using t-butanol and DCC, no racemization of the product was observed. Csanady, G.; Medzihradszky, K. OPPI Briefs. 1988, 20, 180-184.
3. Gibson, F. S.; Park, M. S.; Rapoport, H. J. Org. Chem. 1994, 59, 7503-7507.
4. Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H. J. Am. Chem. Soc. 1995, 117, 4413-4414.
5. Scriven, E. F. V. Chem. Soc. Rev. 1983, 129-161.
6. Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H. J. Org. Chem. 1996, 61, 4560-4567.
7. The coordination number of two has been designated arbitrarily.
8. 3/DMAP: A suspension of 1 (0.5 g, 1.44 mmol), scandium triflate (0.425 g, 0.864 mmol), and DMAP (0.527 g, 4.32 mmol) in anhydrous methylene chloride (50 mL) was cooled to -8°C in an ice-salt bath, followed by the addition of r-Boc-(S)-alanine N-hydroxysuccinimide ester (6, 1.24 g, 4.32 mmol). The reaction mixture was stirred at -8°C for 30 min and allowed to warm to room temperature over 2 h. The reaction mixture was worked up as in method A to give a solid residue which was recrystallized from methanol (70 mL) to provide compound 4 (0.701 g, 94%).