Pal and Mukerjee

Pal and Mukerjee [14] developed another total formal synthesis of racemic pisiferic acid (1) and this is described in Fig. (6). 

The synthesis is lengthy. We believe that the transannular reaction for the introduction of carboxylic acid at annular position is more convenient than the method adopted by Pal and Mukerjee [14]. 

D-Glucosamine hydrochloride and triethylamine added to a soln. of p-nitrophenyl acetate in dimethyl sulfoxide, stirred 1 hr. at room temp., and stored 4 days at 20° N-acetyl-D-glucosamine. Y ca. 100%. - This method is more convenient than previously reported ones. F. e. s. H. Mukerjee and P. R. Pal, J. Org. Chem. 55, 2042 (1970). 

---