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Regioselectivity in the syntheses of Enantiopure 2-Benzopyrans through Intramolecular cyclization of tethered Lactaldehydes. Conformations of the products
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Regioselectivity in the syntheses of Enantiopure 2-Benzopyrans through Intramolecular cyclization of tethered Lactaldehydes. Conformations of the products

R. Aggarwal, A.A. Birkbeck, R.G.F. Giles, I.R. Green, Y. Gruchlik and F.J. Oosthuizen
Australian Journal of Chemistry, Vol.56(5), pp.489-498
2003
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Abstract

Using titanium tetraisopropoxide, the enantiopure tethered lactaldehyde (α′ S,2S)-2-(3′-hydroxy-α′-methyl-benzyloxy)propanal (6) is cyclized with complete regio- and diastereoselectivity ortho to the phenolic hydroxyl group to give (1S,3S,4R)-3,4-dihydro-1,3-dimethyl-2-benzopyran-4,5-diol (7). Similar cyclization of the epimeric (α′ R,2S)-lactaldehyde (25) yields solely the corresponding (1R,3S,4R)-4,5-diol (34). The 4,5-diacetate (26), but not (35), undergoes conformational inversion of the heterocyclic ring through significant 4,5-peri interactions between the adjacent acetoxy substituents. Spontaneous cyclizations of the corresponding phenoxide ions of the lactalde-hydes (6) and (25), generated by fluoride from their silyl ethers, led to the related 4,7-diols with high regioselectivity through ring-closure para to the aromatic oxygen.

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Domestic collaboration
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Citation topics
1 Clinical & Life Sciences
1.219 Cancer Drugs
1.219.1527 Naphthoquinone Derivatives
Web Of Science research areas
Chemistry, Multidisciplinary
ESI research areas
Chemistry
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