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Open AccessArticle

Asymmetric Total Syntheses of Two 3-Acyl-5,6- dihydro-2H-pyrones: (R)-Podoblastin-S and (R)- Lachnelluloic Acid with Verification of the Absolute Configuration of (−)-Lachnelluloic Acid

Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669- 1337, Japan
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Dedication: One of the author (Y.T.) offers his warmest congratulations to Professor Ben L. Feringa (University of Groningen, The Netherlands) on being awarded the 2016 Nobel Prize in Chemistry
Molecules 2017, 22(1), 69; https://doi.org/10.3390/molecules22010069
Received: 20 November 2016 / Accepted: 25 December 2016 / Published: 1 January 2017
(This article belongs to the Special Issue Asymmetric Synthesis 2017)
Expedient asymmetric total syntheses of both (R)-podoblastin-S and (R)-lachnelluloic acid, representative of natural 3-acyl-5,6-dihydro-2H-pyran-2-ones, were performed. Compared with the reported total synthesis of (R)-podoblastin-S (14 steps, overall 5% yield), the present study was achieved in only five steps in an overall 40% yield and with 98% ee (HPLC analysis). In a similar strategy, the first asymmetric total synthesis of the relevant (R)-lachnelluloic acid was achieved in an overall 40% yield with 98% ee (HPLC analysis). The crucial step utilized readily accessible and reliable Soriente and Scettri’s Ti(OiPr)4/(S)-BINOL‒catalyzed asymmetric Mukaiyama aldol addition of 1,3-bis(trimethylsiloxy)diene, derived from ethyl acetoacetate with n-butanal for (R)- podoblastin-S and n-pentanal for (R)-lachnelluloic acid. With the comparison of the specific rotation values between the natural product and the synthetic specimen, the hitherto unknown absolute configuration at the C(6) position of (−)-lachnelluloic acid was unambiguously elucidated as 6R. View Full-Text
Keywords: asymmetric Mukaiyama aldol reaction; asymmetric total synthesis; natural fungicide; 3- acyl-5,6-dihydro-2H-pyrones; 1,3-bis(trimethylsiloxy)diene; podoblastin; lachnelluloic acid; alternaric acid asymmetric Mukaiyama aldol reaction; asymmetric total synthesis; natural fungicide; 3- acyl-5,6-dihydro-2H-pyrones; 1,3-bis(trimethylsiloxy)diene; podoblastin; lachnelluloic acid; alternaric acid
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MDPI and ACS Style

Fujiwara, T.; Tsutsumi, T.; Nakata, K.; Nakatsuji, H.; Tanabe, Y. Asymmetric Total Syntheses of Two 3-Acyl-5,6- dihydro-2H-pyrones: (R)-Podoblastin-S and (R)- Lachnelluloic Acid with Verification of the Absolute Configuration of (−)-Lachnelluloic Acid. Molecules 2017, 22, 69.

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