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SYNTHETIC ROUTES TO CHIRAL AZIRIDINONES (CHIRAL AUXILIARY, ASYMMETRIC INDUCTION)
Abstract
A suitable methodology is outlined for the production of optically active (alpha)-hydroxy amide derivatives utilizing the carbohydrate based derivative D-mannitol as the starting substrate. It is demonstrated that a number of optically enriched C-1 substituted glucopentitols could be obtained from 2,3,4,5-diisopropylidene D-arabonaldehyde obtained from D-mannitol. In each case, a diastereomeric solid is obtained which is suitable for further resolution. A peculiar solvent dependence was noted for the stereospecificity of the t-butyl magnesium chloride additions thereof resulted in a >90% excess of a single diastereomer. This phenomenon was studied as a function of temperature, concentration, counterion as well as under different solvent conditions. A similar study was done with the 2,3-0-isopropylidene-L-glyceraldehyde as the substrate. The addition of t-butylmagnesium chloride also displays a similar solvent dependence with this substrate. The products were determined to result from syn-addition to the arabonaldehyde and anti-addition for the glyceraldehyde. The syn-addition product could be formed with this substrate using t-butylmagnesium chloride under the proper conditions. Relevant models are developed to explain these stereochemical results. A complementary methodology for obtaining optically active (alpha)-hydroxy acid derivatives from the corresponding (alpha)-keto acids in conjunction with a chiral auxiliary agent is outlined. Several chiral auxiliary agents were prepared from D-camphor. L-Pyrrolidine methanol was also used as a chiral auxiliary. A rational model is developed in order to predict the stereoselectivity of the reactions involving these compounds under both chelation and non-chelation control. Several methods for the direct cyclization of the hydroxy amides were investigated with encouraging results. The (alpha)-hydroxy amides were also converted stereospecifically to suitable derivatives for base promoted cyclization to the (alpha)-lactam. Although several bases were employed with success, excellent results are obtained using KH in a suitable solvent.
Subject Area
Organic chemistry
Recommended Citation
MARREN, THOMAS J, "SYNTHETIC ROUTES TO CHIRAL AZIRIDINONES (CHIRAL AUXILIARY, ASYMMETRIC INDUCTION)" (1986). ETD collection for University of Nebraska-Lincoln. AAI8614461.
https://digitalcommons.unl.edu/dissertations/AAI8614461