Synthesis of blood-group substances. 6. Synthesis of O-.alpha.-L-fucopyranosyl-(1 .fwdarw. 2)-O-.beta.-D-galactopyranosyl-(1 .fwdarw. 4)-O-[.alpha.-L-fucopyranosyl-(1 .fwdarw. 3)]-2-acetamido-2-deoxy-.alpha.-D-glucopyranose, the postulated Lewis d antigenic determinant