Amino acids morpholinones

Moloney and co-workers (64) also made use of the morpholinone template in the synthesis of analogues of the kainoid group of amino acids. Treatment of the template under the conditions reported by Harwood furnished the expected adducts. In keeping with earlier observations, the reaction proceeded with complete facial selectivity generating the new C(3) stereogenic center with complete control. 

An alternative multistep approach to the synthesis of a-amino acids, using the boronic acid as the precursor of the carboxylic acid group, was reported by Harwood et al. [56]. Thus, reaction of a chiral morpholinone derivative with furyl boronic acid and various aldehydes gave, in a diastereocontrolled manner, the corresponding adducts which were converted in several steps to the a-amino acids [56],... 

To build up the desired cyclic key precursors, containing an amide bond as an anchor to connect the triazole moiety, different strategies can be pursued. Cyclization of y-amino acids directly yields pyrroli-dones, whereas P-amino alcohols allow access to two different chiral bicyclic frameworks. They can form either oxazolidin-2-ones (Enders and Kallfass 2001) or morpholinones upon treatment with phosgene or chloro acetylchloride, respectively (Scheme 3). 

As illustrated in the aeeompanying proeedure, (N-t-Boe)allylglyeine, this morpholinone has proven to be one of the most versatile and useful ehiral glycine equivalents from which a large variety of amino acids can be prepared. Several other, recent asymmetric electrophilic glycine enolate and cation equivalents have been devised." ... 

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