Automated synthesis of small molecules using chiral, non-racemic boronates
Provided are methods for making and using chiral, non-racemic protected organoboronic acids, including pinene-derived iminodiacetic acid (PIDA) boronates, to direct and enable stereoselective synthesis of organic molecules. Also provided are methods for purifying PIDA boronates from solution. Also provided are methods for deprotection of boronic acids from their PIDA ligands. The purification and deprotection methods may be used in conjunction with methods for coupling or otherwise reacting boronic acids. Iterative cycles of deprotection, coupling, and purification can be performed to synthesize chiral, non-racemic compounds. The methods are suitable for use in an automated chemical synthesis process. Also provided is an automated small molecule synthesizer apparatus for performing automated stereoselective synthesis of chiral, non-racemic small molecules using iterative cycles of deprotection, coupling, and purification.
1. A compound of formula (III)
wherein:
R* is a chiral group
of at least 90% enantiomeric excess;
R 21 and R 22 are independently selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, aralkyl, and heteroaralkyl; or R 21 and R 22 , taken together, form a 5-10-membered cycloalkyl or aromatic ring, or form a 5-10-membered heterocyclic or heteroaromatic ring comprising 1-3 heteroatoms independently selected from the group consisting of O, N, and S;
R 23 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocyclyl, aryl, heteroaryl, aralkyl, and heteroaralkyl;
R 1′ and R 2 are both hydrogen or identically selected (C1-C3)alkyl;
R 3 and R 4 are both hydrogen or identically selected (C1-C3)alkyl; and
m is 0, 1, or 2,
provided that the compound of formula (III) is not
2. The compound of claim 1 , wherein R* is a chiral group of at least 95% enantiomeric excess.
3. The compound of claim 1 , wherein R* is
4. The compound of claim 3 , wherein R* is
5. The compound of claim 3 , wherein R* is
6. The compound of claim 1 , wherein R* is selected from the group consisting of
7. The compound of claim 6 , wherein R* is selected from the group consisting of
8. The compound of claim 6 , wherein R* is selected from the group consisting of
9. The compound of claim 1 , wherein R 21 and R 22 , taken together, form a 5-10-membered cycloalkyl or aromatic ring, or form a 5-10-membered heterocyclic or heteroaromatic ring comprising 1-3 heteroatoms independently selected from the group consisting of O, N, and S.
10. The compound of claim 9 , wherein R* is
11. The compound of claim 10 , wherein R* is
12. The compound of claim 10 , wherein R* is
13. The compound of claim 9 , wherein R* is
14. The compound of claim 13 , wherein R* is
15. The compound of claim 13 , wherein R* is
16. The compound of claim 1 , wherein m is 0.