Stereochemistry of kahalalide F
Isabelle Bonnard1, Ignacio Manzanares, Kenneth L Rinehart
1Roger Adams Laboratory, Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Avenue, Urbana, Illinois 61801, USA. ibonnard@univ-reunion.fr
Abstract:
The stereochemistry of the amino acids in the marine-derived cyclic depsipeptide kahalalide F has been defined by a series of degradation reactions (hydrolysis, ozonolysis, Edman degradation, and Marfey derivatization), yielding smaller fragments of the marine natural product. The results from these reactions agree with the structure originally proposed by Hamann and Scheuer and with the same stereochemistry of most of the component amino acids more recently proposed by Goetz, Yoshida, and Scheuer. However, our assignments of d-Val(3) and l-Val(4) are the reverse of previous assignments made as l-Val(3) and d-Val(4). The present (reversed) stereochemistry is crucial for the antitumor activity of kahalalide F.
Related Concept Videos
Radical Halogenation: Stereochemistry
Halogenation to form a new chiral center:
Acid-Catalyzed α-Halogenation of Aldehydes and Ketones
In the first step of the mechanism, the acid protonates the carbonyl oxygen resulting in a resonance-stabilized cation, which subsequently loses an α-hydrogen to form an enol tautomer. The C=C bond in an enol is highly nucleophilic because of the electron-donating nature of the –OH group. Consequently, the double bond attacks an electrophilic halogen to form a...
E2 Reaction: Stereochemistry and Regiochemistry
When a substrate with two different β hydrogens undergoes an E2 elimination, the presence of a strong base can yield two regioisomeric alkenes. The more-substituted alkene is the major product and...
Aldol Condensation with β-Diesters: Knoevenagel Condensation
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
ortho–para-Directing Deactivators: Halogens


