Carbohydrate-derived 4-pentyn-1-ols have been synthesized from spirocyclic oxirane precursors upon reaction with allenylmagnesium bromide. They undergo cycloisomerization at low-valent chromium or tungsten templates to give spirocyclic 2-oxacyclohexylidene metal complexes. (C) 2000 Elsevier Science S.A. All rights reserved.