Two hexadeuterated brassinosteroids (BS) ([26,27-2H6]-23-dehydroxycastasterone and [26,27-2H6]-cathasterone) containing a hydroxy group at C22 instead of the 22R,23R-diol function characteristic for most compounds of this class were prepared for biochemical studies. The corresponding non-deuterated compounds are considered intermediates in brassinolide biosynthesis. The carbon skeleton of the side chain with proper stereochemistry at C24 was prepared from commercially available (2R)-3-hydroxy-2-methylpropanoate. This low molecular fragment was coupled to the tetracyclic steroidal fragment through the reaction of the appropriate sulfone with C22 aldehyde. Formation of the necessary configuration of the 22-hydroxy group was achieved by hydride reduction of the corresponding ketone. Deuterium atoms at C26 and C27 originated from [2H3]methyl iodide used for alkylation of the intermediate sulfone.
- Labeled compounds
- Plant growth hormone