ChemInform Abstract: Total Synthesis of the Lycopodium Alkaloid (+)‐Serratezomine A.

Abstract

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Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis

“…The photoisomerization of cis-cycloalkenones to trans-cycloalkenones is a well-established procedure. 317−323 An early example of this effect can be found in the photoisomerization of cis-2-cycloheptenone (406) to trans-2-cycloheptenone (407), where irradiation of a mixture of cis-2-cycloheptenone and excess cyclopentadiene (195) at −50 °C gave a single adduct (408) in 95% yield (Scheme 70). 324 Intramolecular Diels−Alder trapping of photochemically generated trans-cyclic enones have also been reported as a rapid entry to complex polycyclic structures (Scheme 71).…”

Cutting-Edge and Time-Honored Strategies for Stereoselective Construction of C–N Bonds in Total Synthesis

“…648 In the synthesis of the Lycopodium alkaloid (+)-serratezomine A, Johnston and coworkers employed a reduction of the iminiun ion to install the required C−N bond (Scheme 157b). 649,650 Starting from imino alcohol 167-4, mesylation and spontaneous cyclization gave iminium ion 157-5, which was reduced to tricyclic amine 157-6/157-7 in 98% yield. However, the broad NMR peaks of 157-6/157-7 precluded a reliable measurement of the diastereoselectivity.…”

Oxidative Carbon−Carbon Bond Formation via Allyldimethylsilyl Enol Ethers

“…Unlike for the simple allyl system (i.e., 5a), replacing NaHCO 3 with 2,6-di-t-butylpyridine led to a further improvement in yield to 83% (Table 1, entry 7). Under these conditions the benzyloxy substituted silyl ether 5c (R ) CH 2 OBn) 9 gave 62% yield of the desired allylated ketone 6c (R ) CH 2 OBn), indicating that functionalized allyl fragments may be employed with this chemistry.…”

“…Si-C and Si-O bond cleavage, along with a second single electron oxidation would then produce the desired adduct 4. 7 Related examples of intermolecular allylation of β-carbonyl imines, 8 and one example of a vinylogous amide 9 allylation of enol ethers with allylsilanes is possible when the silane is part of the ketone (i.e., linked through the carbon backbone rather than the enol oxygen such as in our system). 10 MacMillan and co-workers have elegantly demonstrated the power of their SOMO activation strategy by developing an enantioselective allylation of aldehydes using organocatalysis.…”