Journal
TETRAHEDRON
Volume 67, Issue 3, Pages 641-649Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2010.11.047
Keywords
Friedel-Crafts acylation; Fries rearrangement; O-Acylation; Trifluoromethanesulfonic acid; Homotyrosine
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Funding
- Ministry of Education, Science, Sports and Culture [18032007, 20200038, 19510210, 21510219]
- Grants-in-Aid for Scientific Research [20200038, 21510219, 18032007] Funding Source: KAKEN
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Reactions involving phenol derivatives and acyl chlorides have to be controlled for competitive O-acylations and C-acylations (Friedel Crafts acylations and Fries rearrangements) in acidic condition. The extent for these reactions in trifluoromethanesulfonic acid (TfOH), which is used as catalyst and solvent, is examined. Although diluted TfOH was needed for effective O-acylation, concentrated TfOH was required for effective C-acylations in mild condition. These results have been applied to the novel synthesis of homotyrosine derivatives. Both Fries rearrangement of N-TFA-Asp(OBn)-OMe and Friedel-Crafts acylation of phenol with N-TFA Asp(Cl)-OMe in TfOH afforded the homotyrosine skeleton, followed by reduction and deprotection afforded homotyrosines maintaining stereochemistry of Asp as an optically pure form. (C) 2010 Elsevier Ltd. All rights reserved.
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