- A Simple Synthesis of all four Stereoisomers of 2,2,5-Trimethyl-1,3-dioxolane-4-carbaldehyde
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A simple and efficient procedure for the syntheses of all four stereoisomers of the 2,2,5-trimethyl-1,3-dioxolane-4-carbaldehydes 1a-1d has been developed.Starting with readily available aldopentose diethyl dithioacetals 2, 6, 10 and 14, the title compounds were obtained by a selective protecting group strategy and subsequent Raney-nickel reduction, followed by lead tetraacetate cleavage.This procedure allows an application on a multigram scale. - Keywords. 2,2,5-Trimethyl-1,3-dioxolane-4-carbaldehydes, aldopentose diethyl dithioacetals, lead tetraacetate cleavage.
- Binder, W. H.,Prenner, R. H.,Schmid, W.
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- Versicolactones A and B: Total synthesis and structure revision
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To further determine absolute configurations of versicolactones A and B, total synthesis of versicolactones A and B and their six stereoisomers were reported in this Letter. The 1H and 13C NMR spectra of the synthetic erythro-stereoisomers matched perfectly with those of the natural products. Combined with the comparison of the specific rotations, the absolute configuration of versicolactones A and B were revised as (4Z,6R,7S)- and (4E,6R,7S)- from the corresponding (4Z,6R,7R)- and (4E,6R,7R)-6,7-dihydroxyocta- 2,4-dien-4-lactone, respectively.
- Wang, Liping,Zhu, Weiming
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p. 6729 - 6731
(2013/11/19)
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- Molecular and Crystal Structure of Hyptolide, a Naturally Occurring α,β-Unsaturated δ-Lactone
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Hyptolide, a six-membered, α,β-unsaturated C12 lactone, has been reisolated from Hyptis pectinata Poit.Detailed 1H and 13C NMR spectroscopic studies and a crystal structure determination on the basis of single-crystal X-ray diffraction data collected at 293 K provide evidence for the detailed structure and relative configuration of hyptolide.The crystal structure has been determined from 2261 most significant X-ray intensities and refined to an R factor of 0.065.The space group is P21 and the cell parameters are a = 7.629(2), b = 24.639(3), c = 10.468(2) Angstroem and β = 90.64(2) deg.The absolute configuration is established by synthesis of 10(S),11(R)-dihydroxydodecanoic acid, the enantiomer of an acid previously produced by exhaustive hydrogenation of hyptolide.On the basis of the combined evidence, supported by chiroptical data, hyptolide can now be formulated as 6R-(1Z,3S,5R,6S)-5,6-dihydro-6--2H-pyran-2-one.Its relation to other C12-lactones of natural origin is briefly discussed.
- Achmad, Sjamsul,Hoeyer, Thomas,Kjaer, Anders,Makmur, Lukman,Norrestam, Rolf
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p. 599 - 609
(2007/10/02)
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