Chiral guanidines, salts thereof, methods of making chiral guanidines and salts thereof, and uses of chiral guanidines and salts thereof in the preparation of enantiomerically pure amino acids

A compound having a structure of Formula (I):

• wherein:
• both of the chiral carbon atoms denoted by “*” are both in the R configuration or both in the S configuration;
• G1 is selected from the group consisting of:
• H, C1-C12 unsubstituted alkyl, C1-C12 substituted alkyl, C6-C12 unsubstituted aryl, C6-C12 substituted aryl, unsubstituted (C1-C6 alkylene)-(C6-C12 aryl), substituted (C1-C6 alkylene)-(C6-C12 aryl), C1-C12 unsubstituted heteroalkyl, C1-C12 substituted heteroalkyl, C6-C12 unsubstituted heteroaryl, C5-C12 substituted heteroaryl, unsubstituted hetero[(C1-C6 alkylene)-(C6-C12 aryl)], and substituted hetero[(C1-C6 alkylene)-(C6-C12 aryl)];
• G2 is selected from the group consisting of:
• H, C1-C12 unsubstituted alkyl, C1-C12 substituted alkyl, C6-C12 unsubstituted aryl, C6-C12 substituted aryl, unsubstituted (C1-C6 alkylene)-(C6-C12 aryl), substituted (C1-C6 alkylene)-(C6-C12 aryl), C1-C12 unsubstituted heteroalkyl, C1-C12 substituted heteroalkyl, C5-C12 unsubstituted heteroaryl, C5-C12 substituted heteroaryl, unsubstituted hetero[(C1-C6 alkylene)-(C6-C12 aryl)], and substituted hetero[(C1-C6 alkylene)-(C6-C12 aryl)];
• G3 and G6 are independently selected from the group consisting of:
• H, C1-C12 substituted alkyl, C2-C12 unsubstituted alkyl, C1-C12 substituted heteroalkyl, and C1-C12 unsubstituted heteroalkyl;
• G4 and G5 are independently selected from the group consisting of:
• unsubstituted C6-C12 aryl, substituted C6-C12 aryl, unsubstituted C6-C12 heteroaryl, substituted C6-C12 heteroaryl, unsubstituted [(C6 aryl)-(C1-C6 alkyl)-(C6 aryl)], substituted [(C6 aryl)-(C1-C6 alkyl)-(C6 aryl)], unsubstituted [(C6 aryl)-(C1-C6 heteroalkyl)-(C6 aryl)], and substituted [(C6 aryl)-(C1-C6 heteroalkyl)-(C6 aryl)];
• provided that:
• (i) either:
• (a) at least one of G1, G2, G3, and G6 is not H;
• or
• (b) at least one of G4 and G5 is not phenyl;
• (ii) if G4 and G6 are both or
• or both
• then at least one of G1, G2, G3 and G6 is not H;
• (iii) if G3 and G6 are both H, and G2 is methyl,
• then either G4 and G5 are not both phenyl, or G1 is not NO2, ethyl, tert-butyl, benzyl, cyclohexanyl,
• and
• (iv) if G2, G3, and G6 are all H, and G4 and G5 are both phenyl, then G1 is not H, methyl, ethyl, tert-butyl, phenyl, benzyl, cyclohexanyl,