Sodium acetate phenylglycinate

The key sequence in a somewhat involved stereospecihc total synthesis of a carbacephem starts by preparation of a chiral auxiliary. It is interesting to note that nitrogen is the only atom from this molecule retained in the hnal product. Constmction of this moiety starts with the formation of the carbethoxy derivative (37-2) from L(- -)-phenylglycine (37-1). Selective reduction of the free carboxyl group with borane. THF leads to the hydroxycarbamate (37-3). In a one-pot sequence, this is first cyclized to the corresponding oxazolidinone (37-4) by means of sodium hydride and then alkylated with ethyl bromoacetate (37-5). Saponification of the side chain then affords the chiral acetic acid (37-6). The carboxyl group is then activated by conversion to its acid chloride (37-7). 

This is prepared by reducing a mixture of j8-p-arsinoanilinoethyl alcohol and phenylglycine-p-arsinic acid in hydrochloric acid solution by 50 per cent, hypophosphorous acid in the usual way, or by the use of stamious chloride. The product is deep yellow, does not darken on exposure to the air, and is wholly soluble in sodium bicarbonate. The free base is obtained by converting the above product to its sodium salt and adding acetic acid to the solution. 

An approach to L-tcrt-leucine (9) is based on the use of a cheap chiral template, o-phenylglycine amide (8) in an asymmetric Strecker reaction with pivaldehyde, and HCN generated in situ from sodium cyanide and acetic acid in water gave the aminonitrile 10 in high yield and diastereoisomeric excess (Scheme 9.10)." ... 

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