Stereoselective Total Synthesis of Pyranicin and 4‐Epi‐Pyranicin from Carbohydrate Precursors

The total synthesis of pyranicin and 4-epi-pyranicin has been accomplished from carbohydrate precursors. The general synthetic strategy includes two main fragment formations: (1) THP fragment (2) Butenolide fragment.

Abstract

Herein, we describe a simple and efficient pathway for the total synthesis of pyranicin and 4-epi-pyranicin by utilizing carbohydrates as chiral raw materials for the first time. The general synthetic strategy involves the formation of two main fragments: Fragment 1 is the central tetrahydropyran core, which was constructed in a total of 10 steps from 2,3,4,6-tetra-O-acetyl D-glucal via Ferrier-type rearrangement and oxidative cyclization as the key steps. Fragment 2 is the butenolide fragment, which was obtained in a gram scale with a total of 14 steps from diacetyl-L-rhamnal involving a ring contraction strategy.