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Topic: removing vicinal OH-groups from a steroid-like molecule  (Read 2904 times)

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Offline CsJoe

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removing vicinal OH-groups from a steroid-like molecule
« on: October 29, 2013, 10:31:17 AM »
I have a steroid-like molecule containing 2 vicinal OH-groups (both in beta-configuration) in its A-ring, at the 2,3-position. I'd like to remove these two groups. So far I have already tried tosylation, but with no result at all. The molecule also contains two other OH-groups on another part of the molecule, but they are tertiary OH-groups, which didn't undergo any reaction of the same kind. In the reactions I used methylene-chloride as solvent, 2,2 eqv. (or 4,5 eqv.) of TsCl and 2,5 eqv. of pyridine. I started the reaction at 0°C and let it warm up to room temperature. No matter how long the reaction was going on, no change in the starting material has been observed. Now I tried the same with toluene as solvent at 80°C, but no results either.
Could it be a result of sterical hindrance? Should I try mesylation instead or some other method to remove these OH-groups?
Thank you very much for your answers!  :)

Offline MOTOBALL

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Re: removing vicinal OH-groups from a steroid-like molecule
« Reply #1 on: October 31, 2013, 08:41:14 PM »
Perhaps an organic chemist could comment on the 3rd step of this proposal,

1. React with mesyl chloride (1 equiv)
2. Oxidize the free-OH to >C=O
3. Reduce the >C=O to -OH with NaBH4---will the configuration be inverted to give trans -OH in the molecule described by the OP??

Offline stewie griffin

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Re: removing vicinal OH-groups from a steroid-like molecule
« Reply #2 on: November 20, 2013, 03:01:02 PM »
Sorry for the late reply. What do you mean by "remove these two groups"? Do you want to replace them with hydrogen, or with something else?
I'm assuming you want to replace them with hydrogen. If that is the case, what about a Corey-Winter olefination followed by reduction of the resultant olefin?

Offline CsJoe

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Re: removing vicinal OH-groups from a steroid-like molecule
« Reply #3 on: November 21, 2013, 10:55:44 AM »
Thank you very much! The Corey-Winter olefination seems to be a very good idea! Both the olefin or its saturated alternative can be a valuable target for us.

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