Abstract:
Ocotillol(
3 )and its epimer(
4 )have been synthesized from 20(
S)-protopanaxatriol [20(
S)-PPT] via two routes, and their formation mechanism has been speculated. Route 1: Compounds
3 and
4 were obtained from 20(
S)-PPT by oxidation with
m-CPBA at the yield of 44. 1% and 28. 6%, respectively. Route 2: Compounds
3 and
4 were prepared from 20(
S)-PPT by acetylation, oxidation and saponification at the yield of 16. 4% and 16. 2%, respectively. The formation mechanism of compounds
3 and
4 is speculated as below: 1)The chemical environments of both sides of C24(25)double bond in 20(
S)-PPT are different due to the existence of intramolecular hydrogen bond, which led to the different oxidation ratio of the two sides, and the different yields of compounds
3 and
4 . 2)There is not intramolecular hydrogen bond in acetylated 20(
S)-PPT, and the chemical environments of both sides of C24(25)double bond are similar, which resulted in almost equal yields of compounds
3 and
4 synthesized through oxidation with
m-CPBA, intramolecular
SN2 and saponification.