5‐Bromo‐8‐Nitro‐1‐Naphthoic Acid as Protective Group for Alcohols Under Mitsunobu Conditions

Abstract

The use of the readily available 5‐bromo‐8‐nitro‐1‐naphthoic acid (NNapOH) as a protective group for primary and secondary alcohols is described. Protection is carried out under Mitsunobu conditions, and the protective group can be readily removed under mild reducing conditions, due to the significant steric strain between C‐1 and C‐8 naphthalene substituents. The reaction has been tested with different hydroxy substrates, including monoalcohols, 1,2‐diols, and the anticancer ribonucleoside 5‐fluorouridine. Interestingly, in the case of linear 1,2‐diols, protection occurs preferentially at the secondary alcohol. In addition, orthogonal protection is obtained with N‐Boc hydroxy amino acid derivatives.