Syntheses of Dexamethasone Conjugates of the Phytohormones Gibberellin A3 and 24-Epicastasterone

The syntheses of N-[10-(9alpha-fluoro-11beta,17alpha-dihydroxy-16alpha-methyl-3-oxoandrosta-1,4-diene-17beta-carboxamido)decyl]gibberellamide (7) and 6-[({N-[10-(9alpha-fluoro-11beta,17alpha-dihydroxy-16alpha-methyl-3-oxoandrosta-1,4-diene-17beta-carboxamido)decyl]carbamoyl}methoxy)imino]-24- epicastasterone (10) are described. [(Benzotriazol-1-yl)oxy]bis(pyrrolidin-1-yl)methylium hexafluorophosphate (HBPyU) was used as the coupling agent for the reaction of gibberellic acid as well as of 24-epicastasterone-O-(carboxymethyl)oxime with N-(10-aminodecyl)-9alpha-fluoro-11beta,17alpha-dihydroxy-16alpha-methyl-3-oxoandrosta-1,4-diene-17beta-carboxamide (4). The gibberellic acid conjugate 7 was also synthesised by the coupling of succinimidyl gibberellate 6 with amine 4.