[Dan]

Explain the following reaction sequence, predicting the structure of compound 2.

[stewie griffin]

The first step is a bromolactonization with the carboxylic acid on the right. The remaining -COOH on the left is then converted to a mixed anhydride and reduced with sodium borohydride to the alcohol. Finally the resultant alcohol is BOM protected with BOMCl.

2 is then taken forward. The Zn inserts into the C-Br bond to do an elimination, kicking out -COO^- and reforming the alkene. The next step with the azide material is a bit odd to me. It looks like some weird Staudinger variant but I don't know how we get rid of the carbon from the -COOH and replace it with a nitrogen.
The osmium tetroxide oxidized the olefin to the aldehyde which is then reduced to the alcohol.

[Dan]

Good so far. Almost there.

There is a typo, I apologise, it is diphenylphosphoryl azide (PhO)₂P(O)N₃ (not Ph₂P(O)N₃). It has now been corrected in my original post.

I will give a hint in a couple of days if nobody else comes forward.

[stewie griffin]

Ahh, I've been away from organic chemistry for too long. I would have gotten this quicker two years ago.

The third to last step (step E) is a Curtius rearrangement. Once I drew out the BOC group and realized we had tert-butanol in the mix I finally saw it.

[Dan]

Yes indeed, nicely done.

I will post the full solution when I get time, probably tomorrow, unless you fancy putting your words into pictures?

[stewie griffin]

I may draw it out tonight. The wife takes the TV on Mondays and Tuesdays to watch Dancing with the Stars 
Although I do miss out on Monday night football, the advantage is that I get some quite time to browse the forums and do some reading 

[quimorg]

Hi,
do you have a reference for the the problem,
 my group does literature reviews and  mechanisms, and would like to have it as a mechanism problem for the group.

PS. nicely done Stewie

[Dan]

I have attached the solution (but not with full mechanism).

Taken from Terashima's synthesis of (+)-FR900482

The steps from this problem come from:

Tet. Lett. 1996, 37, 3475 Link

The rest of the synthesis continues:

Tet. Lett. 1996, 37, 3479 Link

The endgame is described in more detail here:

Tet. Lett. 1996, 37, 3471 Link