Abstract: Diels-Alder cyclizations of 2-methyl-2, 8, 1O-undecatrienals (I) were effected at-23 to-13 OC in the presence of alkylaluminum chlorides to afford the endo products I1 and 111 in high yield. An OTBS grouping at C-7 exhibited high diastereocontrol in favor of the syn isomer I11 whereas a C-4 methyl substituent showed complete preference for the anti isomer (IV-V). On the other hand, C-7 methoxy, benzyloxy, or methoxymethyl substituents ...