Casper, David M. Burgeson, James R. Esken, Joel M. Ferrence, Gregory M. Hitchcock, Shawn R. Toward the Development of a Structurally Novel Class of Chiral Auxiliaries:  Diastereoselective Aldol Reactions of a (1<i>R</i>,2<i>S</i>)-Ephedrine-Based 3,4,5,6-Tetrahydro-2<i>H</i>-1,3,4-oxadiazin-2-one Asymmetric aldol addition reactions have been conducted with (1<i>R</i>,2<i>S</i>)-ephedrine-derived 3,4,5,6-tetrahydro-2<i>H</i>-1,3,4-oxadiazin-2-one (<b>2</b>). Diastereoselectivities range from 75:25 to 99:1 for the formation of the crude non-Evans syn adducts <b>8a</b>−<b>h</b>. The facial selectivity of the enolate is directed by the stereogenic N<sub>4</sub>-methyl substituent. Aldol adduct <b>8a</b> is readily cleaved by acid hydrolysis to afford (2<i>S</i>,3<i>S</i>)-3-hydroxy-2-methyl-3-phenylpropionic acid (<b>9</b>) in >95% ee. selectivity;methyl substituent;Auxiliary;Tetrahydro;Asymmetric;ee;Diastereoselectivities range;crude;enolate;tetrahydro;Chiral;syn;formation;stereogenic N 4;Aldol adduct 8;Structurally Novel Class;oxadiazin;acid hydrolysis;Diastereoselective;aldol;hydroxy 2002-09-17
    https://acs.figshare.com/articles/journal_contribution/Toward_the_Development_of_a_Structurally_Novel_Class_of_Chiral_Auxiliaries_Diastereoselective_Aldol_Reactions_of_a_1_i_R_i_2_i_S_i_-Ephedrine-Based_3_4_5_6-Tetrahydro-2_i_H_i_-1_3_4-oxadiazin-2-one/3744216
10.1021/ol026721f.s002