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46. Asymmetric Total Synthesis of (−)-Spirofungin A and (+)-Spirofungin B

Author

Shimizu, T., Satoh, T., Murakoshi, K., and Sodeoka, M.

Abstract

The stereocontrolled total synthesis of (−)-spirofungin A (1) and (+)-spirofungin B (2a), polyketide-type antibiotics having various antifungal activities, has been achieved employing the Weinreb amide 8, the alkyne 9, and the vinyl boronate 5 readily available from the common intermediate 10. The first synthesis proceeded with a longest linear sequence of 31 steps, affording (−)-1 and (+)-2a in 7.9% and 5.2% overall yields, respectively.

Published
2005

47. Amine-Salt-Controlled, Catalytic Asymmetric Conjugate Addition of Various Amines and Asymmetric Protonation

Author

Hamashima, Y., Somei, H., Shimura, Y., Tamura, T., and Sodeoka, M.

Abstract

The combined use of chiral Pd complex 2 and amine salt enabled completely regulated release of free nucleophilic amine. Under these conditions, an efficient catalytic asymmetric conjugate addition of various amines was achieved to afford β-amino acid derivatives in high chemical yields with up to 98% ee. Furthermore, a highly enantioselective protonation in 1,4-addition of amine was also developed.

Published
2004

48. Immobilization and Reuse of Pd Complexes in Ionic Liquid:  Efficient Catalytic Asymmetric Fluorination and Michael Reactions with β-Ketoesters

Author

Hamashima, Y., Takano, H., Hotta, D., and Sodeoka, M.

Abstract

Palladium complexes (1 and 2) were immobilized in ionic liquids, and their applications to catalytic asymmetric fluorination and Michael reaction of β-ketoesters were successfully demonstrated. This immobilization enabled the reuse of the catalysts no less than 10 times in fluorination and 5 times in Michael reaction with levels of efficiency comparable to those obtained in usual organic solvents.

Published
2003

49. Solution-Phase Parallel Synthesis of Carbamates Using Polymer-Bound N-Hydroxysuccinimide

Author

Sumiyoshi, H., Shimizu, T., Katoh, M., Baba, Y., and Sodeoka, M.

Abstract

A convenient method for the synthesis of carbamates using polymer-supported N-hydroxysuccinimide is described. Various carbamates were synthesized in highly pure form without the need for chromatographic purification. This new “catch and release”-type solid-phase synthesis should be useful for combinatorial synthesis of various carbamates.

Published
2002
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50. Synthesis of a Tetronic Acid Library Focused on Inhibitors of Tyrosine and Dual-Specificity Protein Phosphatases and Its Evaluation Regarding VHR and Cdc25B Inhibition

Author

Sodeoka, M., Sampe, R., Kojima, S., Baba, Y., Usui, T., Ueda, K., and Osada, H.

Abstract

Selective inhibitors of protein tyrosine phosphatases (PTPs) and dual-specificity phosphatases (DSPs) are expected to be useful tools for clarifying the biological functions of the PTPs themselves and also to be candidates for novel therapeutics. We planned a library approach for the identification of PTP/DSP inhibitors in which 3-acyltetronic acid is used as a “core” phosphate mimic. A series of novel tetronic acid derivatives were synthesized and evaluated as inhibitors of the dual-specificity protein phosphatases VHR and cdc25B. Several compounds are found to be potent inhibitors of cdc25B, which is a key enzyme for cell-cycle progression. The promising results described herein strongly indicated that this tetronic acid library is potent as a library focused on the PTP/DSP-selective inhibitor.

Published
2001

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