Enantiospecific synthesis of the proposed structure of the antitubercular marine diterpenoid pseudopteroxazole: revision of stereochemistry.
An enantiospecific synthesis of structure 1, previously assigned to the antitubercular marine natural product pseudopteroxazole, has been accomplished as outlined in Scheme 1. Coupling of diene acid 3 and amino phenol 4 produced the amide 5, which was subjected to a novel oxidative intramolecular Diels-Alder reaction to generate the tricyclic lactam 6a stereoselectively. This product was transformed via intermediates 7-11 into the diene 13. Cationic cyclization of 13 afforded two diastereomeric tricyclic amphilectanes which were separated and transformed by parallel four-step sequences into 1 and 2, respectively. Neither 1 nor 2 were identical with pseudopteroxazole, indicating a need for revision of the structure, probably to 16.
Johnson
T W
TW
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Corey
E J
EJ
D000470:Alkaloids / Q000138:chemical synthesis / Q000737:chemistry; D000995:Antitubercular Agents / Q000138:chemical synthesis* / Q000737:chemistry; D001583:Benzoxazoles / Q000138:chemical synthesis / Q000737:chemistry; D003500:Cyclization; D004224:Diterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D010080:Oxazoles; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D000470:Alkaloids; D000995:Antitubercular Agents; D001583:Benzoxazoles; D004224:Diterpenes; D010080:Oxazoles; C433836:pseudopteroxazole; C410139:pseudoteroxazole