Use of a methodology I haven't really heard about in a long time.; the nitrone-cyclopropane cycloaddition. Kerr and coworkers now use it in the synthesis of one of those indolizidine alkaloids, phyllantidine. Fairly straightforward synthesis, although again, I would always pay attention to forming an N-O bond at an early stage. One of my favourite name reactions is used- the Krapcho decarboxylation, the concomitant hydrolysis and decarboxylation of an ester using LiCl in DMSO.
I am too lazy to look up the literature, but why doesn't the nitrone add to the double bond?
Also, the nitrone-cyclopropane addition should be nonconcerted, since we have a nicely stabilised ring opened intermediate.
The other interesting thing is the selectivity of the enolate oxidation.
At first, I was not satisfied, but then I thought that their explanation for it sounds ok. But it looks a little crafty when you draw the vinyl group conveniently pointing in a sterically hindered direction, and make that the only structure with the group in that position! The difference between the group in that position and pointing away from that position is 2 kcal/mol by the way, at least that's what MMFF says for a model compound.
According to Eliel's latest version, the A value for OH ranges from 0.6 to 1.04 for different solvents, while that for CO2CH3 is 1.2-1.3. Also, MMFF gives a difference of 1 kcal/mol for the product with OH axial. So not much difference there, but still worth keeping in mind that the product with the CO2CH3 axial dominates. I wonder how much the reaction is product controlled here though. Such analyses depend on the thermodynamic nature of the reaction; in this case, the fact that the oxaziridine ring opens probably means that the products as a whole are lower in energy. If that is so, then the TS should resemble the reactant, but I would never place my bets on such rationalizing, as subtle effects can change things in the TS. Also there are other factors here, especially the facile nature of topside attack.