Complementary Stereochemical Outcomes in Proline-Based Self-Regenerations of Stereocenters
摘要:
Stereoselective alkylations of proline-based amino amides are described, where high levels of either a cis or trans configuration can be attained simply by the choice of the aminal group. Isobutryaldehyde-derived aminals provide the cis configuration, while 1-naphthaldehyde-derived aminals engender the complementary trans configuration.
An analysis of the complementary stereoselective alkylations of imidazolidinone derivatives toward α-quaternary proline-based amino amides
摘要:
Alkylations of praline-based imidazolidinones are described based on the principle of self-regeneration of stereocenters (SRS), affording high levels of either the cis or trans configured products. Stereoselectivity is dictated solely on the nature of the 'temporary' group, where isobutyraldehyde-derived imidazolidinones provide the cis configured products and 1-naphthaldehyde-derived imidazolidinones afford the complementary trans configured products. These stereodivergent products can be readily cleaved to afford both alpha-alkylated proline enantiomers from readily available L-proline. A series of imidazolidinones were alkylated to investigate the origin of the anti-selectivity. Potential contributions toward the observed anti-selectivity are discussed on the basis of these experiments, suggesting a refined hypothesis for selectivity may be in order. (C) 2015 Elsevier Ltd. All rights reserved.