Synthesis of dl-«-Lipoic Acid 1273 acid.10 The mixture was shaken in an atmosphere of nitrogen for 10 minutes at room temperature and then extracted with a total of 40 ml. of benzene. The benzene extracts were washed consecutively with dilute sodium thiosulfate, 5% sodium bicarbonate, and water, and then evaporated in vacuo. The viscous oil remaining was diluted to 24.3 ml. with benzene and introduced onto a column prepared from a slurry of 150 g. of Florisil in benzene. The results are presented in Table I. The simple procedure described resulted in a 70-fold purification with approximately 40% recovery of active material. Saponification3 of 31.1 mg. of a-ester (233,000 units/mg.) prepared in this manner resulted in 16.4 mg. of crystalline -lipoic acid (250,000 units/ mg.), m.p. 47.5°. The recovery of active material was 56%.The X-ray powder data of this sample of -lipoic acid were identical with those of other samples isolated from acidhydrolyzed liver residue.3
Extensive toxicological studies were carried out to define the probable hazard of octabromobiphenyl (OBB) to workers, users, and the environment. OBB had low acute toxicity in mammals and birds by various routes of administration. It was essentially non-irritating to rabbit eyes, non-irritating to human skin and caused only mild skin irritation and no sensitization in the guinea pig. OBB caused equivocal effects in the rat fetus. OBB was stored in the body fat of rats and caused liver enlargement at high single doses or low repeated doses. The studies indicate probable low safety factors in application and use and probable bioaccumulation. Hexabromobiphenyl (HBB) was more acutely toxic than OBB by skin absorption in the rabbit and caused liver enlargement at lower single doses.
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