2, 3‐Alkadiensäureester als Dienophile; Anwendung bei der Synthese von (+)‐( R )‐Lasiodiplodin

2,3‐Alkadienoates as Dienophiles, Application in the Synthesis of (+)‐( R )‐Lasiodiplodin Methyl 2, 3‐alkadienoates 2 are shown to react at 80° with l, 1‐dimethoxy‐3trimethylsilyloxy‐l, 3‐butadiene (1) to give the adducts 3 in good yields. Rearrangement of 3 , catalyzed by p ‐toluenesulfonic acid or by sodium methoxide, affords the 6‐substituted methyl 4‐hydroxy‐2‐methoxybenzoates 4 (R H, CH 3 , C 6 H 5 ). An analogous reaction sequence starting with (‐)‐(11 R )‐dodeca‐2, 3‐dien‐11‐olide ((‐) ‐6 ) and 1 leads, via the adduct (R)‐7 , to (+)‐( R )‐lasiodiplodin ((+) −8 ) with properties identical to those of the natural product. The allene lactone (‐) ‐6 was prepared by an intramolecular Wittig condensation of ( R ) −5 , produced from (–)‐( R )‐9‐hydroxydecanoic acid.