A synthesis of camptothecin

A total synthesis of camptothecin has been carried out. Central to our synthesis is the intramolecular condensation of a suitably designed ketol, which in turn was obtained from a tricyclic ABC ring synthon. A tandem reductive amination and Michael addition sequence on an unsaturated quinoline ester was employed for the assembly of the ABC skeleton.     

A practical formal synthesis of camptothecin

The synthesis of the DE ring of camptothecin using simple and inexpensive starting materials, employing an addition elimination reaction and selective esterification of an aliphatic carboxylic acid as key steps is described.     

A novel, expeditious synthesis of racemic camptothecin

[reaction: see text] A novel and efficient synthesis of racemic camptothecin, starting from a readily accessible hydroxy pyridone, is presented. Key steps include a Claisen rearrangement of a functionalized allylic ether, a hindered Heck coupling, and a Friedl?nder condensation.     

A short synthesis of ishwarone

2,3,4-Trimethyl-2-cyclohexenone can be converted to the corresponding isoprene Diels-Alder adduct by a sequence initiated by conjugate addition of lithium bis(3-methyl-3-butenyl)cuprate; the sesquiterpenoid ishwarone has been synthesized in two steps from the resulting octalone.     

A short synthesis of praziquantel

The synthesis of praziquantel ( 1 ), a potent anthelmintic agent, is reported. The synthesis requires five steps and proceeds in 16% yield.     

A short synthesis of morachalcone A

Advanced C-prenylated intermediates for three aromatase inhibitors, including morachalcone A, can be synthesized through a Claisen-Schmidt condensation followed by Florisil^®-catalyzed [1,3]-sigmatropic rearrangement of a prenyl phenyl ether.     

A short total synthesis of sulfobacin A

A total synthesis of the von Willebrand factor receptor antagonist sulfobacin A is described. Key steps for this short route to sulfobacin A include ruthenium-catalyzed asymmetric hydrogenation and diastereoselective electrophilic amination for the construction of the three stereogenic centers.     

Total synthesis of camptothecin and SN-38

A new practical and concise total synthesis of enantiopure camptothecin and SN-38 (14% overall yield, 99.9% ee and 99.9% purity) was described, starting from inexpensive and readily available materials. The development of column chromatography-free purification was achieved in all steps, which offers an economic industrial process to the camptothecin-family alkaloids.     

Carboalumination/Ni-catalyzed couplings. A short synthesis of verticipyrone

Verticipyrone (1) has been synthesized in six overall steps from commercially available ethyl-2-methylacetoacetate. This represents the first successful application of a modified Negishi carboalumination-nickel-catalyzed cross-coupling reaction to a chloromethylated pyrone.     

A short synthesis of diastereomeric norambraketals

A short synthesis of diastereomeric norambraketals was accomplished starting from norambreinolide. The reaction of norambreinolide with methyllithium followed by dehydration of the obtained 8α-hydroxy-14,15,16-trinorlabdan-12-one gave 14,15,16-trinorlabd-8(17)-en-12-one. Oxidation of the latter with OsO₄ or peracids with subsequent isomerization of the formed epoxy ketone leads, respectively, to (12R)-8α,12∶12,17- and (12S)-8β,12∶12,17-diepoxy-14,15,16-trinorlabdans. Only the former is fragrant and possesses ambergris odor.     

A short synthesis of (+)-hygrine

The synthesis of the alkaloid hygrine in a series of six steps starting from readily available proline N-methyl derivative (5) is described.     

A short synthesis of bisabolane sesquiterpenes

A facile total synthesis of three members of the bisabolane sesquiterpene family, namely (±)-curcumene, (±)-xanthorrhizol and (±)-curcuhydroquinone had been achieved in high overall yield. The synthesis used bromobenzene derivatives as starting materials. The halogen-lithium exchange followed by addition of isoprenylacetone and reduction of the obtained carbinols are the key steps of the synthetic pathway. This synthetic approach provides a new route to the bisabolane sesquiterpenes.     

A short synthesis of (+)-cyclophellitol

[reaction: see text] A new synthesis of (+)-cyclophellitol, a potent beta-glucosidase inhibitor, has been completed in nine steps from D-xylose. The key transformations involve a zinc-mediated fragmentation of benzyl-protected methyl 5-deoxy-5-iodo-xylofuranoside followed by a highly diastereoselective indium-mediated coupling with ethyl 4-bromocrotonate. Subsequent ring-closing olefin metathesis, ester reduction, olefin epoxidation, and deprotection then afford the natural product. This constitutes the shortest synthesis of (+)-cyclophellitol reported to date.     

A short synthesis of 2,3,4-trihydrodibenzofuranes

Summary Treatment of 2-phenoxypropionic acid with polyphosphoric acid gave substituted benzofuran-3-ones (2a–h), which were converted into 2,3,4-trihydrodibenzofuran-3-ones (4a–h)via the compounds3a–h.Clemmensen reduction of the compounds4a–h gave the 2,3,4-trihydrodibenzofuranes (5a–h).

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Eine einfache Synthese von 2,3,4-Trihydrobenzofuranen

Zusammenfassung Behandlung von 2-Phenoxypropionsäure mit Polyphosphorsäure lieferte die substituierten Benzofuran-3-one (2a–h), welche über3a–h in die 2,3,4-Trihydrodibenzofuran-3-one (4a–h) übergeführt wurden. DurchClemmensen-Reduktion von4a–h wurden die gewünschten 2,3,4-Trihydrobenzofurane (5a–h) erhalten.

     

A short synthesis of 5-methylhistamine

Methoxybromination of 4,5-dihydro-2-methylfuran ( 4 ), followed by treatment of the resulting bromoketal 5 with hot formamide, gave 4-(2-hydroxyethyl)-5-methyl-1H-imidazole ( 3 ) in 25% yield. This method provides easy access to the selective H₂-agonist 4-methylhistamine ( 1 ) via the chloromethyl intermediate 2 .     

A short total synthesis of (+)-furanomycin

[reaction: see text] Furanomycin is a Streptomyces metabolite that substitutes for isoleucine in protein translation. We report a concise and modular synthesis starting from the Garner aldehyde and proceeding in seven steps to furanomycin. The key steps include a stereoselective acetylide addition and the Ag+-mediated cyclization of an alpha-allenic alcohol to construct the trans-2,5-dihydrofuran. The efficiency (12% overall yield) and flexibility of the route will provide ample quantities of furanomycin and analogues for protein engineering.     

A short stereoselective synthesis of (+)-boronolide

A short and stereoselective synthesis of (+)-boronolide via oxidative functionalization of an olefin using a pendant sulfinyl group is described. Diastereoselective allylation was performed using Keck’s protocol and the lactone moiety was prepared by ring closing metathesis.