Improved Synthesis of the Amine Fragment of FR901464 and Thailanstatins through the Development of a Convenient N-Detosylation Method.

FR901464 and thailanstatins are potent cytotoxic natural products that share an amine-containing tetrahydropyran ring. We previously reported the synthesis of the tetrahydropyran component. Here, we changed the protecting group for the amine from Boc to tosyl, improving yields and the time economy. A highlight of the revised synthetic scheme is the use of lithium, t-butanol, and ethylenediamine in THF (nontraditional Birch reduction conditions) for the N-detosylation.