Chemical Correlation of Cistendiol Obtained from Cativic Acid in Two Different Pathways

Abstract

Objective This study aims to convert cativic acid, which was isolated from Ageratina jocotepecana, into cistendiol (5), an analog of cistenolic acid isolated from Cistus symphytifolius. The position of hydroxyl at C-7 in compound 5 could be achieved by applying the Schenck reaction with singlet oxygen (1O2) through photooxidation reaction of 6. Additionally, epoxidation reaction of 1, followed by further reduction and acid treatment, can serve as another pathway to obtain compound 5. Methods Cativic acid was isolated from Ageratina jocotepecana flowers, reduction methodology was realized with THF and LiAlH4, epoxidation reaction was carried out with mCPBA in CH2Cl2 and K2CO3, oxidation of alcohol with PCC in CH2Cl2 and MgSO4, photooxidation reaction was realized with blue and white light using singlet oxygen (1O2) and photosensitizers such as eosin, methylene blue and Ru(bpy)3(PF6)2 in acetonitrile. Geometry optimizations for transition states were performed using MMFF94 with Monte Carlo protocol, and GDFT was used B3LYP/DGDZVP level of theory with Gaussian 09. Results Cistendiol was synthesized by photooxidation reaction of 6 with Ru(bpy)3(PF6)2 and air such oxidant with a ratio of 8:1, while epoxidation of 1 further reduction and acid treatment afforded cistendiol with a ratio of 9:1, the ratio was determined by NMR, additionally the global minimum energy structures GDFT calculated values supports the results described by NMR ratio. The stereochemistry was also confirmed by NOESY experiment and the comparison is in agreement with literature data. Conclusion Herein, we described the conversion of cativic acid isolated from Ageratina jocotepecana employing a new photooxidation methodology and classic epoxidation techniques, to produce an analog of cistenolic acid isolated from Cistus symphytifolius. The results, which include Supplemental material, enable comparison of stereochemistry, specifically the 13 S for C-13 of Ageratina jocotepecana with other compounds such as cistenolic or salvic acid, which had been the subject of study by researchers.