[[V]]

I don't necessarily need to go through the viscinal diol intermediate, so if you can think of a better way I am open to it! This intermediate was just recommended by my prof as a road map.
Some ideas I have for the ring contraction would be a Tiffenaue-Demjanov Rearrangement or a Wolff-Rearrangement. But with either one I would need to get either an amino group or a N2 group alpha to the bottom OH, but I can't seem to find a way to select that position.
I don't know what the R' group is, but if it is rather bulky could I protect the upper hydroxyl with one molar equvalent of a silo protecting group then oxidize the other one and go from there? This solution seems a little sketch to me, so I'm wondering if anyone can point me in a better direction.
This is a part of a bigger assignment, its just this one step I'm stuck on!
Thank you

[orgopete]

The product 3 looks like an aldol product.

[[V]]

The product 3 looks like an aldol product.

I've considered doing a periodate cleavage followed by aldol, but I don't know how I would control the regiochemistry. Any ideas?

I came up with another rather long solution, but it depends on one thing: Can BOTH of those carbonyls be protected with a ketal even though they are part of a conjugated system?

[orgopete]

Given that this was a roadmap problem, then I don't think it will be necessary to work through any elaborate route. I think practically, if you did the period ate cleavage followed by an aldol, the reaction could give a 50:50 mixture or worse (or better). Given that R and R' are not specified, it would be difficult to predict. If I were doing this in the lab, I would just try it. If the yields were even half good, I'd just stop. (If this were for a commercial product, that would be different.)

Given the symmetry of the intermediate, I think selectivity will always be problematic. The Diels-Alder reaction could be attempted with an unsymmetrical diene. You would still need to think out how this would grant the selectivity needed. I'd put down an aldol and ask your professor if he had something else in mind.