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, CH3, C6H5). 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.