Total Synthesis of (−)-Geissoschizol through Ir-Catalyzed Allylic Amidation as the Key Step: OL 2017

Total Synthesis of (−)-Geissoschizol through Ir-Catalyzed Allylic Amidation as the Key Step

The iridium-catalyzed, Zn(OTf)2 promoted asymmetric allylic amidation of a secondary alcohol derived from tryptamine has been utilized to forge a tetrahydro-β-carboline. Based on this key step, a novel, facile, and enantioselective total synthesis of (−)-geissoschizol was achieved in 10 steps.

More Information: http://pubs.acs.org/doi/10.1021/acs.orglett.7b03133

Synthesis of the ABC Substructure of Brevenal by Sequential exo-Mode Oxacyclizations of Acyclic Polyene Precursors: Org Lett 2017

Synthesis of the ABC Substructure of Brevenal by Sequential exo-Mode Oxacyclizations of Acyclic Polyene Precursors

Exploratory studies on the sequential exo-mode oxacyclizations of acyclic polyene precursors have provided a substantial substructure of brevenal, including the fused tricyclic polyether with stereochemical patterns consistent with the AB and BC ring fusions. The synthesis of acyclic substrates featured two variations of Cr(II)/Ni(II) couplings for preparing 1,1-disubstituted allylic alcohols. A sequence of iodine-promoted cycloetherification, base-promoted intramolecular conjugate addition, and mercury-promoted cycloetherification produced the tricyclic substructure.

Synthesis of Alfaprostol and PGF2α through 1,4-Addition of an Alkyne to an Enal Intermediate as the Key Step: OL 2017

Synthesis of Alfaprostol and PGF2α through 1,4-Addition of an Alkyne to an Enal Intermediate as the Key Step

The veterinary drug Alfaprostol and prostaglandin PGF2α have been synthesized in just nine steps. The strategy involved the conjugate addition of an alkyne to a bicyclic enal, available in three steps by a proline-catalyzed aldol reaction of succinaldehyde. In the case of Alfaprostol, this resulted in the shortest synthesis reported to date. For PGF2α, this approach improved our previous route by making the 1,4-addition and ozonolysis more operationally simple

Cyclopropane Intermediates from Insertion Reactions of Platinum–Carbenes: A Route to Heterospiranes: Synlett 2017

Cyclopropane Intermediates from Insertion Reactions of Platinum–Carbenes: A Route to Heterospiranes

Heteroaromatic-anchored enynals with a pendent alkene group were successfully cyclized through a Huisgen-type [3+2] cycloaddition to give a tetracyclic Pt–carbene complex that underwent insertion into the C–H bond in the β-position to give fused cyclopropanes that are otherwise inaccessible. On heating, the cyclopropanes smoothly rearranged to form the corresponding heterospiranes with excellent levels of stereoselectivity and high yields.

Intramolecular Keto Lactam Condensation: A Convenient and Straightforward Approach to Bicyclic Vinylogous Lactams: EJOC 2017

Intramolecular Keto Lactam Condensation: A Convenient and Straightforward Approach to Bicyclic Vinylogous Lactams

Although the aldol condensation is a well-known reaction, the aza-type aldol condensation, namely, the intramolecular condensation of common keto lactams leading to bicyclic vinylogous lactams, is a highly demanding transformation, with potential applications in both organic synthesis and medicinal chemistry. The known methods for this type of cyclization require several steps. In this paper, we disclose a straightforward approach that consists of the in-situ formation of silyl enol ethers with tert-butyldimethylsilyl trifluoromethanesulfonate (TBDMSOTf), lactam activation with triflic anhydride (Tf2O), and a tandem cyclocondensation reaction. The reaction can be run in a one-pot manner or in a two-step fashion, both under mild conditions. The yields for the one-pot version were 52–80 %. In some cases, the two-step version gave higher overall yields (44–85 %) than the one-pot version.