Ever since the visualization of precocene I and I1 (la and lb) as antijuveni! e hormone active compounds, isolated from Ageratum houstonianum, 2 several analogues of precocenes have been~ ynthesized.~ The 2, 2-dimethyl-2H-benzopyran system has been noticed as parent molecule for all of these compounds.
![6,6,7-trimethyl-[1,3]dioxolo[4,5-g]chromene结构式](https://image.chemsrc.com/caspic/489/113949-30-7.png)
