The synthesis of Segment B/C corresponding to the C26 through to the C1 positions of tautomycin was achieved by coupling between Segment B (an epoxide) and Segment C (a sulfone carbanion) in the presence of boron trifluoride etherate (BF3·OEt2). Two routes have been developed in esterification of Segment A with Segment B/C. The first route employed Segment A with furan moiety as masked maleic anhydride