Youichi Nishikawa

Total Synthesis of (±)-Hirsutene via Pd2+-Promoted Cycloalkenylation Reaction

Abstract Beginning with trans -2-methyl-4-cyclohexenecarboxylic acid ( 9 ), a total synthesis of linear triquinane sesquiterpene (±)-hirsutene ( 1 ) has been accomplished. An acid catalyzed intramolecular conjugate addition ( 7→6a ) and a Pd 2+ -promoted highly stereocontrolled cyclization ( 5→4 ) were utilized for the key step of the sequence. Interestingly, some synthetic intermediates exhibited cytotoxicity.

Pd2-promoted cyclization in linear triquinane synthesis total synthesis of (±)-hirsutene

Abstract A sequence leading from trans -6-methyl-3-cyclohexenecarboxylic acid ( 3 ) to the cis, anti, cis - tricyclopentane ring system of the hirsutanes is described in which the key step utilizes an acid catalyzed intramolecular conjugate addition ( 5→6a ) and a Pd 2+ -promoted highly stereocontrolled cyclization ( 7→8 ).

Aphidicolin synthesis. II: An expeditious and efficient formal synthesis of (±)-aphidicolin

Abstract An expeditious and efficient formal total synthesis of an antiviral and antitumor tetracyclic diterpene aphidicolin (1) has been achieved. An intramolecular Heck reaction (7→6) and an intramolecular Diels-Alder reaction (4→3) were utilized for the key steps of the sequence.

An expeditious and efficient formal synthesis of (±)-aphidicolin

Abstract An expeditious and efficient formal total synthesis of antiviral and antitumor tetracyclic diterpene aphidicolin has been developed. An intramolecular Heck reaction ( 3→4 ) and an intramolecular Diels-Alder reaction ( 7→8 ) were utilized for the key step of the sequence.

SYNTHESIS OF A CANCER GROWTH-INHIBITING DITERPENE-STEREOSELECTIVE FORMAL SYNTHESIS OF (+)-APHIDICOLIN

Abstract Stereoselective formal synthesis of the diterpene tetraol (+)-aphidicolin (1) is described employing as key steps the cycloisomerization of the enyne 9 to provide the bicyclo[3.2.1]octane derivative 8 and the intramolecular Diels-Alder reaction of the triene 7 to form the aphidicolane-type ring system. This route is, in principal, highly stereocontrolled and extremely efficient.

ENANTIOSELECTIVE TOTAL SYNTHETIC ROUTE TO (+)-APHIDICOLIN

Enantioselective total synthetic route to (+)-aphidicolin (1) has been described. Cycloisomerization reaction (9→10) and intramolecular Diels-Alder reaction (12→13) were employed for the key steps of the sequence.

Aphidicolin synthesis (I)—formal synthesis of (±)-aphidicolin by the successive intramolecular Diels-Alder reactions

Abstract Formal synthesis of an antitumor and antiviral diterpene aphidicolin ( 1 ) has been achieved. The key steps, 7 →- 6 and 4 → 3 , involve intramolecular Diels-Alder reaction.

Simple design for the construction of complex gibberellin framework—Stereoselective synthesis of a possible key intermediate to GA12 via Pd2+-promoted cycloalkenylation reaction

Abstract A successful design for the construction of C 20 gibberellin framework has been described. The key features of the synthesis are as follows: (a) Pd 2+ -promoted cycloalkenylation reaction ( 6 → 5 ) and (b) intramolecular Diels-Alder reaction ( 4 → 3 ).

Lewis Acid Promoted Tandem [4+2] Cycloaddition-Rearrangement Process — A Simple and Efficient Synthesis of Highly Functionalized Oxabicyclo[3.3.1]nonanes

Catalytic Lewis acid promoted tandem [4 + 2]cycloaddition rearrangement processes of the trienic esters (4), (8) and (9) are reported. The novel tandem reactions proceed under thermal (110°C, aluminum catalyst) conditions and afford the highly functionalized oxabicyclo[3.3.1]nonanes (5), (10) and (11), respectively