K. Shishido

An efficient and highly regioselective intramolecular Mannich-type reaction: A construction of the AEF ring system of aconitine-type diterpene alkaloids

Abstract An efficient and highly regioselective intramolecular Mannich-type reaction has been developed. The utility of the methodology, combined with a stereoselective intramolecular Diels-Alder reaction, for the construction of the AEF ring system of aconitine-type alkaloids has been exemplified.

Tandem electrocyclic-sigmatropic reaction of benzocyclobutenes. 21. A new route to isochroman-3-one-4-spiro-1′-cycloalk-3′-enes

Abstract Thermolyses of the benzocyclobutenylspirolactones, easily derived from 1-cyano-5-methoxybenzocyclobutene, afforded isochroman-3-one-4-spiro-1′-cycloalk-3′-enes in good yields via tandem electrocyclic-sigmatropic reaction of o -quinodimethane.

An efficient synthesis of the naphthalene moiety of neocarzinostatin chromophore

Methyl 2-hydroxy-7-methoxy-5-methyl-1-naphthalenecarboxylate, the methanolysis product of neocarzinostatin chromophore, was efficiently synthesized from 1-cyano-5-methoxy-3-methylbenzocyclobutene employing an electrocyclic reaction of E-o-quinodimethane as the key step.

An efficient total synthesis of (±)-decaline and (±)-vertaline

Abstract An efficient total synthesis of the Lythraceae alkaloids decaline and vertaline via the intermolecular [3+2]cycloaddition is described.

A new synthetic route to 2-hydroxynaphthalene-1-carboxylic acid derivatives. An efficient access to the naphthalene moiety of neocarzinostatin chromophore

Abstract Thermolyses of the 1-carbomethoxy-1-alkenyloxybenzocyclobutenes 4a–d produced the dihydronaphthalenes 7a–d via chemoselective electrocyclic reaction of E-o-quinodimethanes in good yields. Then, 7a,b,d were easily converted to the 2-naphthol 9 (R 1 =R 2 =H) by sequential dehydrogenation and deprotection. The method of conversion developed here has been successfully applied to an efficient synthesis of the methanolysis product 12 of neocarzinostatin chromophore 10 .

Synthetic studies toward antitumor quassinoids. 2. A chiral approach to quassimarin via intramolecular Diels-Alder reaction

Abstract A tricyclic synthon ( 9h ) for quassimarin was synthesized in an optically active form from L-(+)-diethyl tartrate via endo-selective intramolecular Diels-Alder reaction.

Studies on the syntheses of heterocyclic compounds—DXLVIII : Synthesis of a hasubanan ring system from the benzylisoquinoline reticuline

Abstract The synthesis of a cepharamine analogue ( 19 ) from reticuline ( 1 ) by phenolic oxidation is reported. Reticuline was converted into the methine base ( 13b ), whose dihydro compound ( 14c ) was oxidised to the seco-morphinandienone ( 17b ). Michael-type cyclization of 17b , followed by an isomerization of the enone ( 18 ) gave the cepharamine-type compound ( 19 ).

Use of an electrocyclic reaction of o-quinodimethane and an intramolecular Mannich-type cyclisation in diterpene alkaloid synthesis: a synthesis of Nagata's intermediate for (±)-atisine

A synthesis of the tetracyclic amine hydrochloride (2), a pivotal intermediate for Nagatas total synthesis of (±)-atisine, is described. The synthesis commenced with an electrocyclic reaction of the Z-o-quinodimethane (10), generated in situ by thermolysis of the benzocyclobutene (9), leading to the dihydronaphthalene (8). The hydrophenanthrene portion in (2) was elaborated by an intramolecular Diels-Alder reaction of the transient triene (6), which was produced from (8)via a nine-step sequence. The piperidine ring construction was accomplished by employing an intramolecular Mannich-type cyclisation (or an intramolecular iminium-ene reaction) of the hydrochloride (4); the resulting tetracycle (3) was then finally converted into (2) by catalytic hydrogenation. The cis-hydrochloride (27) was similarly converted into the cis-tetracycle (31)via(30), whose structure was established by a single-crystal X-ray analysis, by the same manner.