Vicinal Dihydroxy Ester-Protected Tartaric Acid Derivatives

7 Vicinal Dihydroxy Ester-Protected Tartaric Acid Derivatives 

When tartaric acid (1) is heated with acetic anhydride or benzoyl chloride, the diacetyl tartaric anhydride 720a or the dibenzoyl tartaric anhydride 720b is obtained in excellent yield. 

When 720a is treated with O-benzylhydroxylamine at 0 °C, the hydroxamic acid 724 is produced. The remaining carboxyl group is converted to a tert-hu y ester by the reaction of 725 with tert- m y acetate and perchloric acid. Overall yields for these two steps range from 50-75%. Methanolysis quantitatively removes the two acetate protecting groups to afford diol 

which undergoes a selective monoprotection with 100 mol% r -butyldimethylsilyl chloride and 100 mol% imidazole to provide exclusively the desired 0-benzyl 3-(0-tert-butyldimethylsilyl)-4- rNbutyl-L-tartarohydroxamate (728). Interestingly, reaction of 726 with 100 mol% of er -butyldimethylsilyl chloride and 200 mol% of imidazole affords exclusively the 0-benzyl 2-(0-/er -butyldimethylsilyl)-4-/ r butyl-L-tartarohydroxamate 

Refluxing each of the isolated amides 751 or 752 with 3n HCl in dioxane yields the chiral y-lactones (i )-753 or (5)-754, containing three stereogenic centers, in good yields. Treating (R)- 

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