Glycals in Stereospecific Synthesis. Part 4. Tri‐O‐acetyl‐D‐galactal in the Synthesis of (3Z,6Z,9S,10R)‐cis‐9,10‐Epoxy‐3,6‐heneicosadiene, a Sex Pheromone Component of the American White Butterfly (Hyphantria cunea Drury).