Collect. Czech. Chem. Commun. 2001, 66, 1269-1286

Intramolecular Diels-Alder Cycloadditions of cis-Cyclohexadienediols Derived Enzymatically from (2-Azidoethyl)benzene. Construction of Highly Functionalized Bridged Isoquinoline Synthons

Josef Zezula, Tomáš Hudlický* and Ion Ghiviriga

Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, U.S.A.


(3aR,7aS)-4-(2-Azidoethyl)-2,2-dimethyl-3a,7a-dihydrobenzo[1,3]dioxole (22) was converted in two steps to trienes 23 and 24, which upon heating underwent intramolecular Diels-Alder reactions to give mixtures of isomeric 11,11-dimethyl-5-oxo-10,12-dioxa-4-azatetracyclo[,6.09,13]pentadec-14-ene-7-carboxylates 25, 26 and 27, 28, respectively. These products were separated and identified. For comparison, intermolecular Diels-Alder cycloaddition of diene 22 with maleic anhydride was carried out. Products of this reaction, 1-(2-azidoethyl)-4,4-dimethyl-3,5,10-trioxatetracyclo[,6.08,12]tetradec-13-ene-9,11-diones (29 and 30) were converted to methyl ester analogues of 31 and 32 in a two-step sequence. The stereochemical outcome of these cycloadditions is discussed as well as their possible utilization in organic synthesis, especially in total synthesis of some alkaloids.

Keywords: Biotransformations; Diels-Alder reactions; Bridged octahydroisoquinolones; Morphine; Asymmetric synthesis; Isoquinoline alkaloids; Total syntheses; Chemoenzymatic synthesis.

References: 61 live references.