189013-53-4Relevant articles and documents
Synthesis of new naturally occurring 6-deoxo brassinosteroids
Takatsuto, Suguru,Watanabe, Tsuyoshi,Fujioka, Shozo,Sakurai, Akira
, p. 901 - 924 (2007/10/03)
New naturally occurring 6-deoxo brassinosteroids, 6-deoxoteasterone 1, 3-dehydro-6-deoxoteasterone 2 and 6-deoxotyphasterol 3 as well as 6-deoxocastasterone 4, have been synthesized from (20S)-20-formyl-6β-methoxy-3α,5-cyclo-5α-pregnane 5.The key reactions for the construction of the (22R,23R,24S)-side chain of these C28 brassinosteroids are the reaction of the 22-aldehyde 5 with a Grignard reagent derived from (Z)-1-bromo-1-propene, orthoester Claisen rearrangement of the resulting (22S,23Z)-allylic alcohol, and the asymmetric dihydroxylation of the crinosterol dide chain.Regeneration of a 5-en-3β-ol system in A/B-ring followed by catalytic hydrogenation provided 6-deoxoteasterone 1, which was converted to the methanesulfonate 11.Inversion of configuration of the 3β-hydroxyl group and introduction of the 2-ene functionality were achieved by reaction of the sulfonate 11 with potassium superoxide and with lithium carbonate, respectively.The inverted 3α-alcohol 12 was deprotected to afford 6-deoxotyphasterol 3.The alcohol 12 was oxidized to give, after deprotection, 3-dehydro-6-deoxoteasterone 2.Introduction of a 2α,3α-diol group into the 2-ene 14 with osmium tetroxide was followed by deprotection to afford 6-deoxocastasterone 4.
