2-Thiazolidinone: a novel thiol protective surrogate of complete atom efficiency, a practical synthesis of (+)-biotin

2-Thiazolidinone derivatives were shown to be novel protective surrogates of a thiol group in l-cysteine derivatives. After elaboration at the C-4 substituent, the thiol group was completely liberated by simple heating in DMF whose atom efficiency is 100%. A practical synthesis of (+)-biotin was accomplished by the use of the strategy employing 4-functionalized 2-thiazolidinone derivatives as the intermediates, allowing a synthesis of (+)-biotin in 10 steps and in 31% overall yield. Short steps, high yield, and ease of operation of the present approach would permit the hitherto most efficient access to (+)-biotin.