Studies toward the total synthesis of naturally occurring pyranonaphthoquinones from Ventilago harmandiana

The enantioselective synthesis of a naturally occurring pyranonaphthoquinone isolated from a Thai endemic plant, , has been achieved. L-Rhamnose and gallic acid were used as the starting materials. A new -1-glycosidation of L-rhamnal with trimethyl aluminum in the presence of a catalytic amount of y...

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Published in:Pure and applied chemistry 2012-02, Vol.84 (6), p.1435-1443
Main Authors: Kongsriprapan, Sopanat, Kuhakarn, Chutima, Deelertpaiboon, Pramchai, Panthong, Kanda, Tuchinda, Patoomratana, Pohmakotr, Manat, Reutrakul, Vichai
Format: Article
Language:English
Subjects:
Aluminum
annulations
Aromatic compounds
asymmetric synthesis
Catalysis
Deactivation
Enantiomers
Gallic acid
Hauser cycloannulation
Lithium
Lithium chloride
Lithium t-butoxide
phenylsulfanyldifluoromethane
pyranonaphthoquinone
Reagents
stannic chloride
Synthesis
Ytterbium
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Summary:The enantioselective synthesis of a naturally occurring pyranonaphthoquinone isolated from a Thai endemic plant, , has been achieved. L-Rhamnose and gallic acid were used as the starting materials. A new -1-glycosidation of L-rhamnal with trimethyl aluminum in the presence of a catalytic amount of ytterbium(III) triflate was developed. A new reagent, PhSCF H/SnCl , for the formylation of partially deactivated and hindered aromatic compounds has been introduced. Phenylthiophthalide was used efficiently as a cycloannulating agent in the Hauser cycloannulation reaction, employing slightly excess lithium -butoxide as a base with a catalytic amount of lithium chloride. The synthetic route developed is applicable for the synthesis of other analogues with substituents at the aromatic and pyran rings.
ISSN:0033-4545
1365-3075
DOI:10.1351/PAC-CON-11-08-24