Second Generation Total Synthesis of (–)‐Preussochromone D

Kerste, Eric; Beller, Marc Paul; Koert, Ulrich

doi:10.1002/ejoc.202000465

Cited by 8 publications

(10 citation statements)

References 35 publications

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“…Our ongoing interest in the synthesis of chromone-based natural products previously led to the synthesis of preussochromone D ( 2 ) . In addition, we also pursued the total synthesis of 1 because of its intriguing structural features and its biological activity.…”

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confidence: 68%

Total Synthesis of (−)-Preussochromone A

2020

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All non-aqueous reactions were carried out using flame-dried glassware under argon atmosphere. All solvents were distilled by rotary evaporation. Solvents for non-aqueous reactions were dried as follows prior to use: THF was distilled from Solvona®. CH2Cl2 was distilled from CaH2. MeOH and DMF were purchased from Acros Organics in extra dry quality and stored under an argon atmosphere over MS 4 Å. Toluene was distilled from Solvona®. DMSO was dried over CaSO4 overnight, distilled from CaH2 and stored over MS 4 Å. All commercially available reagents and reactants were used without purification unless otherwise noted.Reactions were monitored by thin layer chromatography (TLC) using Merck Silica Gel 60 F254-plates and visualized by fluorescence quenching under UV-light. In addition, TLC-plates were stained using a ceric sulfate/phosphomolybdic acid stain. Chromatographic purification of products was performed on Merck Silica Gel 60 (230-400 mesh) unless otherwise noted using a forced flow of eluents. Concentration under reduced pressure was performed by rotary evaporation at 40 °C and appropriate pressure and by exposing to fine vacuum at room temperature if necessary. NMR spectra were recorded on a Bruker AV 300 MHz, AV III 500 MHz, AV III HD 500 MHz spectrometer at room temperature. Chemical shifts are reported in ppm with the solvent resonance as internal standard. Data are reported as follows: s = singlet, d = doublet, t = triplet, q = quartet, quint = quintet, m = multiplet.Mass spectra were recorded by the mass service department of the Philipps-Universität Marburg. HR-ESI mass spectra were acquired with an LTQ-FT mass spectrometer (Thermo Fischer Scientific). The resolution was set to 100 000. IR spectra were recorded on a Bruker IFS 200 spectrometer. The absorption bands are given in wave numbers (cm -1 ), intensities are reported as follows: s = strong, m = medium, w = weak, br = broad band.Melting points were determined on a Mettler Toledo MP70 using one end closed capillary tubes.Diastereomeric ratios were accurately determined by integration of 1 H-NMR spectra.Optical rotations were determined at 20 °C for the Na-D wavelength (589 nm) with a Krüss P8000 T polarimeter. Absorption coefficient 2.366 mm -1 F(000) 560 Data collection: Diffractometer type STOE STADIVARI Wavelength 1.54186 Å Temperature 100(2) K Theta range for data collection 4.530 to 75.466°. Index ranges -10<=h<=12, -13<=k<=13, -16<=l<=9Data collection software X-Area Pilatus3_SV 1.31.127.0 (STOE, 2016) [2] Cell refinement software X-Area Recipe 1.33.0.0 (STOE, 2015) [3] Data reduction software X-Area Integrate 1.71.0.0 (STOE, 2016) [4] X-Area LANA 1.68.2.0 (STOE, 2016) [5] Solution and refinement: Reflections collected 24893Independent reflections 6509 [R(int) = 0.0201] Completeness to theta = 67.686° 99.3 % Observed reflections 6337[I > 2σ(I)]Reflections used for refinement 6509 Absorption correctionSemi-empirical from equivalents [5] Max. and min. transmission 0.4452 and 0.2044 Flack parameter (absolute struct.) 0.011(11) [6] Larges...

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confidence: 68%

Total Synthesis of (−)-Preussochromone A

2020

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“…The overall yield of preussochromone D ( 10 ) increased to 15% (4% with the old route) and the material throughput could be raised drastically. 13b…”

Section: Synthesis and Structural Revision Of Preussochromones E And Fmentioning

confidence: 99%

“…In order to start the route towards the trans -configured preussochromones, we chose to revisit the early game of our previous synthesis of preussochromone D ( 10 ). 13b Although the enantioselective 1,4-addition gave good yields and ee, it required over-stoichiometric amounts of Lewis acid (1.2 equiv) and the following hydroboration gave a poor d.r. of ~2:1 with reduction of the benzylic ketone.…”

Section: Synthesis and Structural Revision Of Preussochromones E And Fmentioning

confidence: 99%

Synthetic Studies on Chromone Natural Products: The Preussochromones

Koert¹,

Beller²

2022

Synthesis

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The preussochromones are a family of chromone based natural products. Total syntheses of preussochromone A, D, E & F and structural revisions of preussochromone E & F are reviewed, demonstrating the use of α-ketoester and α,β-diketoester as valuable reactants in stereoselective, cyclization reactions in total synthesis. For preussochromone D, E, and F, with their annulated, fully substituted cyclopentane ring intramolecular chromanone-aldol reactions are used as key steps. Key step for the synthesis of the thiopyranchromenone preussochromone A is the addition of a thioketene acetal substructure to an α-ketoester. Developments and improvements are highlighted, which led to the efficient syntheses in this unique group of natural products. 1 Introduction 2 The Route to Preussochromone D 3 Synthesis and Structural Revision of Preussochromone E & F 4 Total Synthesis of Preussochromone A 5 Conclusion

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“…47 Similarly, condensation of the 2 0 ,6 0 -dihydroxyacetophenone with ethyl formate in the presence of sodium ethoxide followed by acidification led to the synthesis of 5-hydroxychromone in excellent yield, on decagram scale. 48 Basha et al developed a methodology to prepare 2,3-unsubstituted chromones from 2 0 -hydroxyacetophenones, via one-carbon extension, using 2,4,6-trichloro-1,3,5-triazine (TCT)/DMF complex. Thus, 2 0hydroxyacetophenones and boron trifluoride diethyl etherate (BF 3 ÁEt 2 O) was cooled to 10 °C and DMF was added dropwise to the reaction mixture.…”

Section: Synthesis Of 23-unsubstituted 4h-chromen-4-onesmentioning

confidence: 99%