Racemic boronolide (1) is prepared in six steps in 4.4% overall yield from acrolein dimer 6 and 1-(trimethyl-silyl)hex-1-yne (8). The latter, by hydromagnesiation, is condensed with 6 to give the corresponding threo-allylic alcohol 13 (Scheme 2). Conversion of 13 to the erythro-allylic alcohol 5 (Scheme 3), bis-hydroxylation, and acetylation afford 1.