The glycosidic precursor of (Z)-5-ethylidene-2(5H)-furanone in Halocarpus biformis juvenile foliage

A new glycosidic lactone, (5R,6R)-5-(1-hydroxyethyl)-2(5H)-furanone beta-D-glucopyranoside, has been identified as the principal precursor of (Z)-5-ethylidene-2(5H)-furanone in juvenile foliage of the New Zealand tree Halocarpus biformis. Three related lactone glycosides were isolated in smaller amounts, together with the known phenolic glycosides pyroside, arbutin and picein. The principal lactone glycoside underwent facile elimination of glucose, in neutral or basic conditions, to yield (2)-5-ethylidene-2(5H)-furanone and its E-isomer. This lactone glycoside was also detected in foliage of H. bidwillii and H. kirkii.