Hetero-bis-metalated 1,3,5-hexatrienes are employed in the linchpin coupling of synthetic fragments for the convergent construction of the central pentaene of the antifungal agent 2‘-O-methylmyxalamide D and its (6E) isomer. Sequential Stille and Suzuki−Miyaura couplings interpolate the boron/tin triene into the pentaene chain. The total synthesis of O-methylmyxalamide D and its (6E) isomer was accomplished efficiently.

A ring-closing metathesis-based strategy has allowed access to an unreported pair of pyridoisoindolones and their previously unknown sultam counterparts. The synthetic routing takes advantage of the ready availability of N-allylphthalimide and N-allylsaccharin and proceeds via the proper incorporation of small side chains into the heterocyclic ring. Positionally selective introduction of the conjugated diene functionality was realized efficiently. Detailed study of the excited-state chemistry of 7 and 8 showed both lactams to be subject to [4 + 2] dimerization under acetone-sensitized conditions. Different regioselectivities are involved, with the response of 8 being far more efficient than that exhibited by 7. No dimers could be isolated from the photolyzates of 9 and 10 under any conditions. While the latter sultam undergoes extensive polymerization, 9 is transformed via direct irradiation at 350 nm into 46 and 47 via [1,3]-sigmatropy involving the S-N bond and heterocyclic ring cleavage, respectively.

Enantioselective approaches to the construction of four complex building blocks of the structurally intricate marine macrolide known as spongistatin 1 are presented. The first phase of the synthetic effort relies on a practical approach to a desymmetrized, enantiomerically pure spiroketal ring system incorporating rings A and B. Concurrently, the C17–C28 subunit, which houses one-fifth of the stereogenic centers of the target in the form of rings C and D, was assembled via a composite of stereocontrolled aldol condensations. Once arrival at the entire C1–C28 sector had been realized, routes were devised to provide two additional highly functionalized sectors consisting of C29–C44 and C38–C51. A series of subsequent transformations including cyclization of the E ring and hydroboration to afford the B-alkyl intermediate for the key Suzuki coupling to append the side chain took advantage of efficient stereocontrol. Ultimately, complete assembly and functionalization of the western EF sector of spongistatin was thwarted by an inoperative Suzuki coupling step intended to join the side chain to the C29–C44 sector, and later because of complications due to protecting groups, which precluded the complete elaboration of the late stage C29–C51 intermediate.

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Fused pyridine derivatives R 0450 Effective Synthetic Routes to 4H-and 10bH-Pyrido[2,1-a]isoindol-6-ones. -Synthesis of compound (X) occurs via a novel twofold dehydrobromination involving an N-acylaminium ion that experiences regiocontrolled hydration. -(DURA, R. D.; MODOLO, I.; PAQUETTE*, L. A.; Heterocycles 74 (2007) 1, 145-148; Evans Chem. Lab., Ohio State Univ., Columbus, OH 43210, USA; Eng.) -K. Woydowski 26-152