Synthesis of a trans-fused tricyclic ether using a novel differentially protected glucal

The construction of the hans-fused 7,6,6-ABC fragment (3) of ciguatoxin 3C, starting from the novel carbohydrate derivative 3-O-benzyl-4-O-tert-butyld imethylsiryl-6-O-triyl-D-glucal, is reported. The formation of the A- and C -rings can be effected by executing two individual ring-closing metathesis steps in a sequential or a one-pot procedure.