I don´t think the proposed degradation to an aldehyde followed by imine and Grignard is the way of choice to do it. Otherwise this would have become more popular by now.
Aromatic acetaldehydes are rather sensitive and tend to give messy mixtures...
But! Has any bee experience with esterification of amino acids?
Once I had to esterify l-prolin, tried to do so with some alcohol and lots of p-toluenesulfonic acid. The product, an oil (as freebase), seemed o.k. and we thought we had it, apart from the fact that it wouldn´t react at all the way we intended it to do and then we decided it was probably something else.
The reason why I go at length into this question is of course that it would be too nice to prepare the esters of phenylalanine and tryptophane and to remove the OH group reductively to yield the corresponding aminoalkyl sidechain.
There is a really wonderful way to reduce esters to the corresponding alcohols by treatment with NaBH4/anhydrous LiCl in THF. Yields about 100%! In case THF is difficult to get even Isopropanol works but part of the NaBH4 gets lost due to side-reaction and the reduction is not so complete.
Now what could be done with the resulting amino alcohol?
Is there a simple way to reduce the CH2OH group to the CH3?
Something like protecting the NH2 and esterifying the OH group with p-toluenesulfonic acid chloride, which upon reduction with LiALH4 should leave a methyl group. What would happen if the unprotected NH2 was reacted to the sulfonamide and this was subjected to the LiAlH4 reduction?
Will a hydrolyzable N-S-bond be the consequence? Or if the amino alcohol was treated with SO2Cl2? Will it form a cyclic
product which upon reduction gives the aminoalkyl-chain?
Any bee with information on this?
