[willug]

Hello all,

I've been thinking about some Horner-Wadsworth-Emmons reactions today, and have come a bit stuck by way of rationalising their stereoselectivity (see attached scheme). We've made a number of these dehydroamino acids en route to non proteinogenic amino acids, and in our system, all of the dehydroamino acids have been afforded exclusively as the Z isomers (by NOE's and a couple of X-ray structures).

The question of course is why. Does anyone know of any models or literature to rationalise this? I can't say much about the R' group over the internet unfortunately. Although I'm not sure what effect that has in any case.

Any ideas would be much appreciated! Thanks  

[Babcock_Hall]

I am a little out of my depth, but I found a link that I thought might be helpful.  http://www.chem.harvard.edu/groups/myers/handouts/15_Horner-Wadsworth.pdf