Furfural is converted to suitably substituted AB synthon 21 for 12a-deoxypillaromycinone in 10 steps by a sequence involving the following key steps: intramolecular Diels-Alder reaction of a furan, 5-endo-trig cleavage of the oxabicyclo adducts 18, and catalytic hydrogenation of the double bond of a tetrasubstituted enone to produce 19. Enones 21a and 21b obtained by dehydrogenation of 19a and 19b, respectively, are then annulated with ethyl 2-methoxy-6-methylbenzoate in a four-step procedure to generate tetracyclic products 25 in 14 steps from furfural.
糠醛经过10个步骤转化为适当取代的AB合成子21,用于制备12a-去氧柱霉素酮。这个过程包括以下关键步骤:糠醛的分子内Diels-Alder反应,氧杂双环加合物18的5-内环三角裂解,以及四取代烯酮的双键催化氢化生成19。通过19a和19b的脱氢,获得烯酮21a和21b,然后用乙酸2-甲氧基-6-甲基苯酸乙酯进行四步反应,生成四环产物25,从糠醛开始共需14个步骤。