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Chemistry Forums for Students => High School Chemistry Forum => Chemistry Olympiad and other competitions => Topic started by: discodermolide on April 23, 2014, 02:12:49 PM

Title: Practice problem 2
Post by: discodermolide on April 23, 2014, 02:12:49 PM

The last step in the synthesis of discodermolide is an acid cleavage of the silyl ether protection and cyclisation shown here.
The second picture shows two of the side products isolated.
Propose a mechanism for the formation of compounds 1 and 2

Title: Re: Practice problem 2
Post by: Rutherford on April 23, 2014, 03:34:40 PM

Tough one. I propose this:

Title: Re: Practice problem 2
Post by: discodermolide on April 23, 2014, 10:36:53 PM

Both look fine to me.
Here is my proposition for number 2, it is sometimes better to redraw the structure and then things may become more evident.
I would guess that water leaves first and you get an allylic carbonium ion.
So I think its back to you now for the next one ;D