No abstract

mp 127 °C).The ester DL-2h can be saponified to DL-phenylalanine as follows. Sodium hydroxide (6 N, 4.5 mL, 27 mmol, 3 equiv) was added to 2.00 g (8.71 mmol) of DL-2h and the mixture was stirred at room temperature for 2 h. The pH of the solution was adjusted to the isoelectric point with 1 N HC1 to obtain 1.17 g (81%) of crystalline DL-phenylalanine, mp 268-271 °C dec (lit.16 mp [271][272][273] °C dec).The Schiff base DL-3h can be converted directly to the amino acid by refluxing a mixture of DL-3h (4.00 g, 11.2 mmol) in 20 mL of 6 N HC1 under argon for 6 h. The solution was cooled and washed several times with ether, and the layers were separated. Water and excess HC1 were removed from the aqueous layer, distilled water was added, and the aqueous solution was taken to the isoelectric point with aqueous NaOH to yield 1.69 g (91%) of DL-phenylalanine, mp 250-251 °C dec (commercial sample, U.S.

H‐D‐Austauschreaktionen werden an den Keto‐sulfiden (II) bzw. (IV) im Vergleich zu den Ketonen (I) bzw. (III) untersucht.

Chlorkohlensäureester (I) bzw. (IV) reagieren mit Natriumthiosulfat zu den wasserlöslichen Alkoxycarbonylthjosulfaten (III) bzw. entsprechenden Bis‐Verbindungen (V), die wasserlöslich sind und zur Acylierung eingesetzt werden können.