Synthesis and preliminary evaluation of dimeric-28-homobrassinosteroids for plant growth regulators

- Preparation of (22R, 23R)- and (22S, 23S)-homocastasterone are reported.
- Nucleophilic additions of C6 carbonyl group by allylic Grignard reagent were designed.
- Olefin metathesis of the allyl analogues using Grubbs catalyst resulted in the dimeric analogues.
- Rice lamina inclination assay of the dimeric analogues showed the significant activity compared to the natural 28-homocastasterone.

Preparation of synthetic analogues of 28-homobrassinosteroids is reported. Also, the addition of the 28-homocastasterone at the C6 carbonyl group via allyl Gringard reagent followed by olefin cross metathesis resulted in dimeric analogues. Rice lamina inclination assay showed that the replacement of the C6 carbonyl group by 6α-allyl and 6β hydroxyl groups led to a decrease in bioactivity, whereas the dimeric analogues showed a reduced but significant bioactivity when compared to the 28-homocastasterone.

The synthesis and bioactivity of the synthetic analogues of 28-homobrassinosteroids including the dimeric compounds of 28-homocastasterone were studied. Evaluation of the rice lamina inclination activity revealed that the dimeric analogues possessed a reduced but significant bioactivity when compared to the nature 28-homocastasterone.