Systematic study of the transition metal-catalyzed aldol reactions of certain prochiral ketones with methyl isocyanoacetate has been made. High diastereoselectivity (80-98% de) of these condensations, leading to methyl (4R*,5R*)-4,5-dihydro-5,5-(disubstituted)-4-oxazolecarboxylates was shown to be controlled by the nature of both catalyst and substituents on the starting ketone.
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Acknowledgment. We thank the JSPS Foundation (Japan), Ministry of Education, Japan, for a Grant-in-Aid for Scientific Research, Uehara Memorial Foundation, International Science Foundation (U6M000, U6M200), INTAS (Network 93-799) for partial financial support of this work.