Does the parol evidence rule apply to a stock agreement as the principal transaction?

In short, defendants' reliance upon the parol evidence rule is misplaced, for the stock agreement and not the requirements contract was the "principal transaction." Mitchill v. Lath, supra; see also Fogelson v. Rackfay Construction Company, 300 N.Y. 334, 338, 90 N.E.2d 881, 882-83 (1950). Indeed, it would appear that the parol evidence rule simply has no application in these circumstances; the oral agreement does not serve to vary or modify the engagement of the parties with respect to the terms of purchase of box materials.