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Optical rotation computation, total synthesis, and stereochemistry assignment of the marine natural product pitiamide A

Ribe, S and Kondru, RK and Beratan, DN and Wipf, P (2000) Optical rotation computation, total synthesis, and stereochemistry assignment of the marine natural product pitiamide A. Journal of the American Chemical Society, 122 (19). 4608 - 4617. ISSN 0002-7863

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Abstract

We report the joint application of ab initio computations and total synthesis to assign the absolute configuration of a new natural product. The expected specific rotations of the (7S,10R)- and (7R,10R)-isomers of pitiamide A in a CHCl3 solvent continuum model were determined as +8 and - 39, respectively, by CADPAC calculations of the electric-dipole-magnetic- dipole polarizability tensor. Total syntheses of these two stereoisomers of the marine metabolite were achieved by a convergent strategy that utilized Evans' oxazolidinone alkylation, a novel water-accelerated modification of Negishi's zirconocene-catalyzed asymmetric carbometalation as well as an unusual segment condensation via Mitsunobu alkylation of a nosyl-activated amide. The experimental optical rotation measurements confirmed the results of the computational optical rotation predictions. On the basis of NMR comparisons, the configuration of pitiamide A was assigned as (7R,10R). These studies highlight the considerable structural significance of [α](D) data, but, because the optical rotation of the natural product was different from either synthetic diastereomer, our work serves also as an illustration of potential problems with obtaining accurate experimental [α](D) data for natural samples.


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Details

Item Type: Article
Status: Published
Creators/Authors:
CreatorsEmailPitt UsernameORCID
Ribe, S
Kondru, RK
Beratan, DN
Wipf, Ppwipf@pitt.eduPWIPF
Date: 17 May 2000
Date Type: Publication
Journal or Publication Title: Journal of the American Chemical Society
Volume: 122
Number: 19
Page Range: 4608 - 4617
DOI or Unique Handle: 10.1021/ja9945313
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Refereed: Yes
ISSN: 0002-7863
Date Deposited: 22 Jul 2015 14:20
Last Modified: 22 Jun 2021 12:55
URI: http://d-scholarship.pitt.edu/id/eprint/25622

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