Synthesis of Optically Pure 2,3,4,5-Substituted Tetrahydrofurans from a Bis-Allylic Framework via an Osmylation-Haloetherification Sequence

Saitô, Seiki; Morikawa, Y.; Moriwake, Toshio

doi:10.1055/s-1990-21151

Cited by 19 publications

(4 citation statements)

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“…[12] In the depicted conformation the "outsides" of the olefinic faces are homotopic, so that it does not matter which of the olefins is attacked first. A similar conformation also explains the diastereoselective course in the hydroxylation of one of the double bonds of (21) [13] and in the cycloaddition with 1,3-dienes, [14] such as cyclopentadiene. It is obvious that compounds of type (19) and (21) are very easily accessible by a two-dimensional synthesis from the appropriate tartaric acid or from D-mannitol [15] [cf.…”

Section: Dmerentiation Of Homotopic Groupsmentioning

confidence: 74%

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Group Selective Reactions

Maier¹

1995

Organic Synthesis Highlights II

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Section: Dmerentiation Of Homotopic Groupsmentioning

confidence: 74%

“…breaking of the C,-symmetry requires reagent control; differentitin can deliver either enantimer with high ee x x (13) differentiation requires only monofunctionalization…”

Section: Simultaneous Synthesis In Two Directionsmentioning

confidence: 99%

Group Selective Reactions

Maier¹

1995

Organic Synthesis Highlights II

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“…A two-step sequence through deprotection of the acetal with TsOH, followed by Wittig reaction [ 27 ], afforded unsaturated ester (1 S )- 13 . After reduction of the ester to an allylic alcohol, tetrahydrofuran (1 S )- 14 was successfully obtained by bromoetherification with NBS in a highly diastereoselective manner [ 28 , 29 , 30 , 31 ] without loss of the bromoallene functionality. The treatment of (1 S )- 14 with TBSOTf and 2,6-lutidine provided silyl ether (1 S )- 8 after the less hindered TBS ether was selectively removed under mild acidic conditions [ 32 ].…”

Section: Resultsmentioning

confidence: 99%

Assignment of Absolute Configuration of Bromoallenes by Vacuum-Ultraviolet Circular Dichroism (VUVCD)

et al. 2021

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A new application of vacuum-ultraviolet circular dichroism (VUVCD), which enables the measurement of CD spectra in the vacuum-ultraviolet region (140–200 nm), for the assignment of the absolute configurations of bromoallenes is described. Bromoallene moieties are found in natural products obtained from many marine organisms. To date, the absolute configuration of bromoallenes has been assigned almost exclusively with Lowe’s rule, which is based on specific rotation. However, exceptions to Lowe’s rule have been reported arising from the presence of other substituents with large specific rotations. For the unambiguous assignment of the absolute configuration of the bromoallene moiety with its characteristic absorption wavelength at 180–190 nm due to the π–π* transition, VUVCD was applied to four pairs of bromoallene diastereomers prepared by modifying the synthetic scheme of omaezallene. The VUVCD spectra clearly showed positive or negative Cotton effects around 180–190 nm according to the configuration of the bromoallene employed, revealing the potential of VUVCD for determining absolute stereochemistry.

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“…While we could not find direct literature precedent for selective mono-AD on 2,6-dienoates, there was literature precedent for monodihydroxylation of this type of substrate under Upjohn conditions. 8 Additionally, we hoped that in situ Michael reaction of the initially formed AD product would remove the potentially reactive second alkene before any second dihydroxylation could take place. For the cyclisation step, we envisaged that the desired 5-exo-trig cyclisation mode would be kinetically preferred over the alternative possible 6-exo-trig.…”

Section: Pergamon Tetrahedron Lettersmentioning

confidence: 99%