Liphagal enantiomers and their derivatives and precursors, and enantioselective methods of making the same
Enantioenriched compositions of liphagal and its derivatives and precursors include more than 50 mol % of a first enantiomer based on the total amount of a first and a second enantiomer. A method of making an enantioenriched composition includes catalytic enantioselective alkylation, ring expansion, and intramolecular aryne cyclization.
1. A method for preparing a compound of Formula 17A:
comprising treating a compound of Formula 17B:
under [2+2] photocycloaddition conditions with a compound represented by the Formula (I):
R 29 R 30 (1)
wherein:
R 8 -R 16 and R 24 are independently selected from hydrogen, alkyl group and carbonyl group;
R 21 and R 28 are hydrogen; and
R 29 and R 30 are independently hydrogen or trialkylsilyl group.
2. A method for preparing a compound of Formula 18A:
comprising treating a compound of Formula 18B:
under [2+2] photocycloaddition conditions with a compound represented by the Formula (I):
R 29 R 30 (1)
wherein:
R 8 -R 16 and R 24 are independently hydrogen or an alkyl group;
R 21 and R 28 are hydrogen; and
R 29 and R 30 are independently hydrogen or trialkylsilyl group.
3. The method of claim 1 or 2 , wherein R 24 is hydrogen.
4. The method of claim 1 or 2 , wherein the compound of Formula (I) is trimethylsilyl acetylene.
5. The method of claim 1 or 2 , wherein the photocycloaddition conditions comprise UV radiation.
6. The method of claim 1 or 2 , wherein the UV radiation comprises UVB radiation.
7. The method of claim 1 or 2 , wherein the photocycloaddition conditions comprise a solvent.
8. The method of claim 7 , wherein the solvent comprises acetone.
9. The method of claim 1 or 2 , wherein the method further comprises treating a compound of Formula 17A or 17B with a Lewis acid.