High 1,4-syn-induction in the addition of chiral allyltrichlorostannanes to chiral aldehydes

Dias, Luiz C.; Giacomini, Rosana; Meira, Paulo R. R.; Ferreira, Edı́lson; Ferreira, Andréa A.; Díaz, Gaspar; Santos, Débora Ribeiro dos; Steil, Leif

doi:10.3998/ark.5550190.0004.a24

Cited by 6 publications

(2 citation statements)

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“…The stereochemistry of the major cyanohydrin ( 6b ) can be rationalized by the Felkin–Ahn transition state model (Figure 3). 24 It suggests a balance between conformers A and B 25 . Thus, it was expected that the use of a bulky N ‐protective group (Boc) would hinder the formation of the N–H bond, favoring the formation of conformer B .…”

Section: Resultsmentioning

confidence: 99%

Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

et al. 2021

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An interesting protocol for stereoselective synthesis of (À)-cytoxazone and its unnatural stereoisomer (+)-5-epi-cytoxazone from D-4-hydroxyphenylglycine in overall yields of 10% and 16%, respectively, is described. The stereoselective addition of cyanide to an N-Boc protected aminoaldehyde (tert-butyl ((R)-1-(4-methoxyphenyl)-2-oxoethyl)carbamate) (5) constitutes the key step in this approach, producing a mixture of cyanohydrins 6a and b (1,2-anti and 1,2-syn tert-butyl (2-cyano-2-hydroxy-1-(4-methoxyphenyl)ethyl)carbamate) in 89% yield, with reasonable stereoselectivity (1.0:1.8) in favor of the anti-Felkin product (1,2-syn). A one-pot sequence of three successive steps from this mixture produced the oxazolidinone isomers 9a and b ((4R,5R)-and (4R,5S)-4-(4-methoxyphenyl)-2-oxooxazolidine-5-carboxylate). Chromatographic column separation and reduction of the ester function of both precursors led to (À)-cytoxazone and (+)-5-epi-cytoxazone.

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Section: Resultsmentioning

confidence: 99%

Stereoselective synthesis of (−)‐cytoxazone and its unnatural congener (+)‐5‐epi‐cytoxazone

et al. 2021

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“…At this stage, the stereodirected introduction of the C5 stereocenter was envisaged by using a stereoselective allylstannylation . The unstable β-hydroxy aldehyde was directly treated with a solution of allylSnCl 3 in CH 2 Cl 2 at −78 °C (prepared from allyltrimethylsilane and SnCl 4 at rt) and was transformed to the syn -1,3-diol 39 (74% yield, two steps from 38 ) (Scheme ). The origin of the chiral induction giving the syn -diol in this reaction is not clear.…”

Section: Third Strategy6mentioning

confidence: 99%