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Seijiro Hosokawa

Publications and source records attributed to Seijiro Hosokawa.

7 recordsLinked to original sources
PubMed2006

Enantioselective total synthesis of convolutamydines B and E.

[reaction: see text] The first enantioselective total synthesis of convolutamydines B and E has been achieved using our vinylogous Mukaiyama aldol reaction. The synthesis features highly diastereoselective vinylogous Mukaiyama aldol reaction with isatin instead of aldehydes to construct a chiral center of convolutamydines. Additionally, the absolute configuration of natural convolutamydine B has been determined as R by its CD spectrum.

Animals↗
PubMed2006

Total syntheses of polyketide-derived bioactive natural products.

Recent progress of total syntheses in our laboratory has been described along with our background and methodologies. The target bioactive polyketides are classified into three categories according to their structures: (i) lactone-fused polycyclic compounds [(+)-cochleamycin A, (+)-tubelactomicin A, and (-)-tetrodecamycin], (ii) aromatic compounds [(-)-tetracycline, (-)-BE-54238B, lymphostin, and (-)-lagunamycin], and (iii) acyclic polyketides [xanthocillin X dimethylether, (+)-trichostatin D, and (+)-actinopyrone A]. Features of the total syntheses are described. Original methodologies have been developed and applied to construct the inherent structures of the target molecules. Most syntheses cited herein are the first total syntheses, and the absolute structures of the target molecules have been determined.

Alkaloids↗
PubMed2004

Acetoxyl group directed cyclization promoted by SmI2: directing group determined stereocomplementarity.

Complete reversal of diastereoselectivity was observed in the SmI(2)-promoted ketyl-olefin coupling cyclizations of the hydroxy ketone or aldehyde and its acetate. For example, the stereodivergent synthesis of the epimeric five-membered-ring alcohols 2 and 4 has been accomplished through the SmI(2)-induced ketyl-olefin coupling cyclizations of the delta-hydroxy ketone 1 and delta-acetoxy ketone 3.

Journal Article↗
PubMed2004

Remote asymmetric induction with vinylketene silyl n,o-acetal.

A highly regio- and diastereoselective TiCl4-mediated vinylogous Mukaiyama aldol reaction using the chiral vinylketene silyl N,O-acetal has been developed. The present vinylogous Mukaiyama aldol reaction provides a unique and effective means of controlling remote asymmetric induction. The methyl group at the alpha-position is important in achieving a high level of stereoselectivity. From a synthetic point of view, this methodology can provide a one-step construction of delta-hydroxy-alpha,gamma-dimethyl-alpha,beta-unsaturated carbonyl unit that is seen in many natural polyketide products.

Journal Article↗
PubMed1999

Mirror Image Synthesis of Left Ends of Ciguatoxin and Gambiertoxin 4b.

Three compounds related to the AB fragments of ciguatoxin and gambiertoxin 4b and two diastereomers (at the C-2 position) of the ABC fragment of ciguatoxin have been synthesized in enantiomeric form. The stereochemistry of the C-2 position was introduced selectively from the corresponding pentose derivative. Construction of the A ring with its side chain was completed by Nicholas type cyclization of an acetylene bis(cobalthexacarbonyl) complex followed by reductive decomplexation.

Journal Article↗