73198-90-0Relevant academic research and scientific papers
68. Enantio- and Diastereoselective Aldol-Reaction of 2,6-Dimethylphenyl Propionate Using Titanium-Carbohydrate Complexes
Duthaler, Rudolf O.,Herold, Peter,Wyler-Helfer, Susanne,Riediker, Martin
, p. 659 - 673 (2007/10/02)
Chloro(cyclopentadienyl)bis(1,2:5,6-di-O-isopropylidene-α-D-glucofuranos-3-O-yl)titanium (1) is used for the transmetallation of Li-enolates obtained from propionyl derivatives.While such Ti-enolates of ketones and hydrazones appear to be unreactive, the
ACYCLIC STEREOSELECTION-13; ARYL ESTERS: REAGENTS FOR THREO-ALDOLIZATION
Heathcock, Clayton H.,Pirrung, Michael C.,Montgomery, Stephen H.,Lampe, John
, p. 4087 - 4095 (2007/10/02)
Preformed Li enolates of hindered aryl esters condense with aldehydes to give predominantly threo aldols.The method has been explored with esters 3 (DMP propionate), 4 (BHT propionate), 5 (DBHA propionate).DMP propionate reacts with benzaldehyde and α-unbranched aliphatic aldehydes to give threo:erythro ratios of about 6.5:1.However, with α-branched aliphatic aldehydes, ester 3 gives only threo-aldols.BHT propionate and DBHA propionate give only threo-aldols with all aldehydes studied.The DMP aldols may be converted into β-hydroxy acids by simple hydrolysis with KOH in aqueous methanol.BHT aldols cannot be hydrolyzed without retroaldolization.However, these aldols can be reduced to diastereomerically pure 1,3-diols.The DBHA aldols can converted into β-hydroxy acids by a method involving oxidation with ceric ammonium nitrate (CAN) in aqueous acetonitrile.Threo-selectivity is also seen in the condensations of DMP butyrate (15), DBHA butyrate (16), DMP pentenoate (17), and BHT pentenoate (18).The approach has been utilized in a stereoselective synthesis of racemic methyl corynomycolate.
Acyclic Stereoselection. 8. A New Class of Reagents for the Highly Stereoselective Preparation of threo-2-Alkyl-3-hydroxycarboxylic Acids by the Aldol Condensation
Pirrung, Michael C.,Heathcock, Clayton H.
, p. 1727 - 1728 (2007/10/02)
threo-3-Hydroxy-2-methylcarboxylic acids may be prepared in high stereochemical yield by condensing aryl propionates 1 or 2 with aldehydes followed by hydrolytic or oxidative removal of the aryl group.
