The Wittig condensation of (2R,3R,4E)-2,6-dimethyl-3-trimethylsilyloxy-4-heptenyltriphenylphosphorylidene with aldehyde 1 produced the desired cis olefin 11 in 45% yield. Treatment of this intermediate with pyridinium tosylate in methanol effected spiroketalization and desilylation with hydrogen fluoride-pyridine in THF afforded the avermectin-nemadectin hybrid 2.
The Wittig condensation of (2R,3R,4E)-2,6-dimethyl-3-trimethylsilyloxy-4-heptenyltriphenylphosphorylidene with aldehyde 1 produced the desired cis olefin 11 in 45% yield. Treatment of this intermediate with pyridinium tosylate in methanol effected spiroketalization and desilylation with hydrogen fluoride-pyridine in THF afforded the avermectin-nemadectin hybrid 2.