The mono-and di-iodo derivatives of 1-oxaspiro [2, 5] bicycloocta-4, 7-diee-6-one, 8 and 9, reacted readily with 3, 5-diiodo-l-tyrosine at pH 8.0 to give 3, 5, 3′-triiodo-l-thyronine (T3) and thyroxine in 70% and 94% yields respectively. In turn, 8 and 9 were prepared by the sodium bismuthate oxidation of their corresponding iodinated p-hydroxybenzyl alcohol derivatives, 6 and 7 in 32% and 37% yields.