143245-40-3Relevant academic research and scientific papers
Studies on the synthesis of bafilomycin A1: Stereochemical aspects of the fragment assembly aldol reaction for construction of the C(13)-C(25) segment
Roush, William R.,Bannister, Thomas D.,Wendt, Michael D.,Jablonowski, Jill A.,Scheidt, Karl A.
, p. 4275 - 4283 (2007/10/03)
Highly stereoselective syntheses of aldols 8a-c corresponding to the C(13)-C(25) segment of bafilomycin A1 were developed by routes involving fragment assembly aldol reactions of chiral aldehyde 6a and the chiral methyl ketones 7. A remote chelation effect plays a critical role in determining the stereoselectivity of the key aldol coupling of 6a and the lithium enolate of 7b. The protecting group for C(23)-OH of the chiral aldehyde fragment also influences the selectivity of the lithium enolate aldol reaction. In contrast, the aldol reaction of 6a and the chlorotitanium enolates of 7a,c were much less sensitive to the nature of the C(15)-hydroxyl protecting group. Studies of the reactions of chiral aldehydes with Takai's (y-methoxyallyl)chromium reagent 40 are also described. The stereoselectivity of these reactions is also highly dependent on the protecting groups and stereochemistry of the chiral aldehyde substrates.
The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride. The merged stereochemical impact of α- and β-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles
Evans,Allison,Yang,Masse
, p. 10840 - 10852 (2007/10/03)
A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral β-hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of β-alkoxy and β-silyloxy aldehydes bearing only an α- or a β-stereogenic center. Examination of the chelated intermediates for α,β-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the α- and β-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the α- and β-positions exhibit variable and unpredictable selectivity.
A stereochemical model for merged 1,2- and 1,3-asymmetric induction in diastereoselective Mukaiyama aldol addition reactions and related processes
Evans, David A.,Dart, Michael J.,Duffy, Joseph L.,Yang, Michael G.
, p. 4322 - 4343 (2007/10/03)
A systematic investigation of the direction and degree of stereoselectivity in aldol addition reactions is presented involving achiral unsubstituted metal enolate and enolsilane nucleophiles and chiral aldehydes. The BF3·OEt2 mediate
