Stereoselective reduction of chiral trans-3-acetyl-4-alkylpyrrolidin-2-ones
摘要:
A number of trans-3-acetyl-4-alkylpyrrolidin-2-ones 8a-d and 11a,b were prepared and reduction of the keto group, carried out with KBH4 in CH3OH, led mainly to 3-hydroxyethylpyrrolidin-2-ones 13a-d and 19a,b with high stereoselection, Configuration of the newly formed stereogenic centre on the hydroxyethyl chain was assigned by H-1 NMR data supported by molecular mechanic calculations and eventually confirmed by X-ray diffraction analysis of p-iodobenzoate derivative 15. (C) 1999 Elsevier Science Ltd. All rights reserved.
trans-3-Acetyl-4-alkyl pyrrolidin-2-ones 5a,b and 8a,b undergo reductive amination with NaBH3(CN) in CH3OH in the presence of CH3COONH4. By acylation of the reaction product the corresponding 3-acylaminoethylpyrrolidin-2-ones 9a-c and 10a,b were obtained with total stereoselection. The configuration of the newly formed stereogenic centre at C-1" of the acylaminoethyl chain was assigned on the basis of H-1 NMR data supported by both molecular mechanics and quantomechanical calculations. (C) 2003 Elsevier Ltd. All rights reserved.