Kin Ichi Tadano

Stereoselective total syntheses of (−)-desoxoprosopinine and (−)-desoxoprosophylline : palladium(O)-catalyzed intramolecular N-alkylation for the key piperidine ring formation

Abstract Intramolecular N -alkylation of D-glucose-derived substrate 21 E proceeded in an S N 2′ mode smoothly in the presence of a Pd(O)catalyst and n -Bu 4 NI. The major cyclization product, a 2,6-dialkylated piperidine 22 t , was effectively converted into the title alkaloids.

(+)-Isoaltholactone: A furanopyrone isolated from Goniothalamus species

(+)-Isoaltholactone, (2S,3S,3aR,7aS)-3-hydroxy-2-phenyl-(2H,3aH)-furano[3,2-b]pyran-5-one was isolated from stembark of Goniothalamus malayanus, stembark and leaves of G. montanus and roots of G. tapis.

Total syntheses of (+)- and (-)-pestalotiopsin A.

An enantioselective total synthesis of both enantiomers of caryophyllene-type sesquiterpenoid pestalotiopsin A has been achieved, thereby establishing the absolute stereochemistry of natural (+)-pestalotiopsin A. Highlights of the synthesis include a [2 + 2] cycloaddition of N-propioloyl Oppolzers camphorsultam and ketene dialkyl acetal and subsequent highly stereoselective 1,4-hydride addition/protonation, an aldol reaction of functionalized bicyclic lactone with aldehyde, an efficient intramolecular Nozaki-Hiyama-Kishi (NHK) reaction for the construction of the highly strained (E)-cyclononene ring, and a palladium-catalyzed reduction of allylic mesylate with retention of the E configuration.

Total Synthesis of (+)-Clavilactone A and (−)-Clavilactone B by Ring-Opening/Ring-Closing Metathesis

The enantioselective total synthesis of natural enantiomers of clavilactones A and B has been achieved. A key feature of the synthesis is the use of a ring-opening/ring-closing metathesis, which allows the one-pot transformation of a strained cyclobutenecarboxylate into a γ-butenolide.

Synthesis of nitrogen- and oxygen-bridged seven- to ten-membered carbocycles using metathesis reactions

This review describes the synthesis of nitrogen- and oxygen-bridged seven- to ten-membered carbocycles using metathesis reactions and their applications to natural products synthesis achieved in the past decade.

Total synthesis of (-)-mniopetal F, a novel inhibitor of RNA-directed DNA-polymerases

Abstract We have achieved a total synthesis of (−)-mniopetal F, a drimane-type sesquiterpenoid which inhibits the reverse transcriptase activity of the human immunodeficiency virus (HIV)-1. The key step in our enantiospecific synthesis is a stereoselective intramolecular Diels–Alder reaction, in which the π-facial selectivity is controlled by the stereoelectronic effect of a trialkylsilyloxy substituent existing adjacent to the dienophile part.

Isolation of a novel substrate-competitive tyrosine kinase inhibitor, desmal, from the plant Desmos chinensis

In the course of a screening program for tyrosine kinase inhibitors, the chloroform extract of a tropical plant, Desmos chinensis, strongly inhibited the enzyme activity. The active substance was purified by silica gel, gel filtration, and finally crystallized. The structure was elucidated by mass spectrometry and X‐ray crystallography to be 8‐formyl‐2,5,7‐trihydroxy‐6‐methylflavanone, and we named it desmal. Desmal competed with peptide substrate and non‐competed with ATP. It inhibited tyrosine kinase in situ in epidermal growth factor (EGF) receptor‐overexpressing NIH3T3 (ER 12) cells. It also inhibited EGF‐induced inositol phosphate formation and morphological changes.

Total Synthesis of (+)-Cytosporolide A via a Biomimetic Hetero-Diels–Alder Reaction

The first total synthesis of (+)-cytosporolide A was achieved by a biomimetic hetero-Diels-Alder reaction of (-)-fuscoatrol A with o-quinone methide generated from (+)-CJ-12,373. The dienophile, highly oxygenated caryophyllene sesquiterpenoid (-)-fuscoatrol A, was synthesized from the synthetic intermediate in our previous total synthesis of (+)-pestalotiopsin A. The o-quinone methide precursor, isochroman carboxylic acid (+)-CJ-12,373, was synthesized through a Kolbe-Schmitt reaction and an oxa-Pictet-Spengler reaction. The hetero-Diels-Alder reaction of these two compounds proceeded with complete chemo-, regio-, and stereoselectivity to produce the complicated pentacyclic ring system of the cytosporolide skeleton. This total synthesis unambiguously demonstrates that natural cytosporolide A has the structure previously suggested.

A total synthesis of (+)-eremantholide A

Abstract Stereoselective and enantiospecific total synthesis of (+)-eremantholide A ( 1 ) is described. The present total synthesis features 1) regio- and stereoselective radical carbocyclization of D-glucose-derived γ-lactone 7 , and 2) a nine-membered ring formation by the coupling reaction of bicyclic triflate 18 and known furanone 19 followed by a vinylogous aldol reaction.

Total synthesis of (+)-vibsanin A

The first total synthesis of (+)-vibsanin A, an 11-membered vibsane diterpenoid, was achieved, unambiguously establishing its relative and absolute stereochemistry. Highlights of the synthesis include the stereoselective formation of an all-carbon quaternary stereocenter by a zinc-mediated Barbier-type allylation in an aqueous medium, and the efficient construction of an 11-membered ring skeleton by a combination of an intramolecular Nozaki-Hiyama-Kishi (NHK) reaction and a Mitsunobu reaction.