An Application of Electrocyclic Reaction for the Synthesis of Pyridoindole Alkaloids

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1.The first enantioselective total synthesis of (R)-(-)-pyridindolol K2 together with its enantiomer was established in a nine-step or ten step sequence based on the construction of β-carboline N-oxide through the thermal electrocyclic reaction of a 1-azahexatriene system involving the indole 2, 3-bond or the thermal cyclization of 3-ethynylindole-2-carbaldehyde oxime, followed by the Sharpless asymmetric 1, 2-dihydroxylation. In addition, the asymmetric total syntheses of (R)-(-)-pyridindolol K1 and (R)-(-)-pyridindolol were also completed using the same starting material.2.A total synthesis of α-carboline alkaloid, mescengricin has been investigated by the construction of α-carboline framework based on the thermal electrocyclic reaction of 2-azahexatriene system involving the indole 2, 3-bond. The construction of the glycerolester and the δ-lactone part at the 4-and 2-positions of α-carboline nucleus were established using 7-demethoxy-α-carboline, respectively. We are now investigation of a total synthesis of mecsengricin using 7-methoxy-α-carboline framework.3.The absolute configuration of (+)-oxopropaline D was determined as R-configuration by the asymmetric synthesis of (R)-(+)-oxopropaline D acetonide.