The novel monocyclic dienediyne 2, which is a simplified analogue of the neocarzinostatin chromophore (1), was synthesized from D-xylitol via conversion of the keto-aldehyde 13 into the highly strained 10-membered ring compound 14 by a simple intramolecular aldol condensation as the key step. The mode of cycloaromatization of 2 by a thiol addition, reminiscent of the chemistry of 1, was also demonstrated.