Total synthesis and stereochemical revision of the chlorinated sesquiterpene (±)-gomerone c

Revised: the total synthesis of gomerone C results in revision of the stereochemical assignment at C3. The synthetic strategy relies on a late-stage Conia-ene reaction, which efficiently forms the bicyclo[3.2.1]octane containing the bridgehead chloride and generates an exocyclic olefin, which can be used as a flexible handle for further elaboration. The two contiguous quaternary centers are installed by means of a Diels-Alder reaction.

Cyclohexyne cycloinsertion in the divergent synthesis of guanacastepenes

The guanacastepenes are a family of 15 diterpenes that share a common 5-6-7 tricyclic core, which is decorated with quaternary centers, unsaturation, hydroxyl and carbonyl groups. Some of these natural products show interesting antimicrobial potency. Their collective structural and biological features have stirred up vibrant activity among organic chemists. Herein, we disclose an account of our studies toward the synthesis of a number of guanacastepenes. The synthetic strategy relies on the use of cyclohexyne in a cycloinsertion reaction to rapidly construct the guanacastepene core. Isolation of a cyclobutenol as intermediate in the cyclohexyne cycloinsertion provided us with the possibility to study further the reactivity of this metastable compound, and we uncovered novel rearrangements and ring-opening reactions. Stereoselective, late-stage oxidative diversification of the carbon scaffold allowed the synthesis of guanacastepenes N and O and paved the way for the synthesis of guanacastepenes H and D.

Enantioselective allylic thioetherification: the effect of phosphoric acid diester on iridium-catalyzed enantioconvergent transformations

You'll take the high road and I'll take the low road: Enantioenriched allylic thioethers have been synthesized from chiral racemic allylic alcohols. The combination of an Ir-(P,alkene) complex and dibutyl phosphoric acid are required to attain high selectivities. Mechanistic studies uncover an enantioconvergent transformation in which substrate enantiomers react along different pathways to give the same product (see scheme; cod=1,5-cyclooctadiene).

Total synthesis of (-)-dendrobine

Cascading to alkaloids: an 18-step total synthesis of (-)-dendrobine is based on a reaction cascade with a key amine group. The amine is the initiator of the cascade and provides an efficient method for installing the stereocenters at C11 and C3. The overall transformation occurs stereoselectively only when the conversion is carried out without the isolation of intermediates.

Total synthesis of (-)-dendrobine

Cascading to alkaloids: an 18-step total synthesis of (-)-dendrobine is based on a reaction cascade with a key amine group. The amine is the initiator of the cascade and provides an efficient method for installing the stereocenters at C11 and C3. The overall transformation occurs stereoselectively only when the conversion is carried out without the isolation of intermediates.

Total synthesis and stereochemical reassignment of (±)-indoxamycin B

Revised version: the first total synthesis of indoxamycin B leads to a stereochemical reassignment of the natural product. The synthetic route features an efficient carboannulation sequence to rapidly access the dihydroindenone system. Moreover, a series of Au(I)-catalyzed transformations served in the construction of the sterically congested core framework.

Expanding the azaspiro[3.3]heptane family: synthesis of novel highly functionalized building blocks

The preparation of versatile azaspiro[3.3]heptanes carrying multiple exit vectors is disclosed. Expedient synthetic routes enable the straightforward access to these novel modules that are expected to have significance in drug discovery and design.

Synthesis of novel azaspiro[3.4]octanes as multifunctional modules in drug discovery

Step-economic and scalable syntheses of novel thia-azaspiro[3.4]octanes are reported. These spirocycles and some related intermediates can serve as uncharted multifunctional modules for drug discovery chemistry.

Probing the role of the mycosamine C2'-OH on the activity of amphotericin B

A synthetic route to a mycosamine donor was designed and provided access to a set of AmB derivatives targeted to probe the effect of the C2'-OH. It was determined that the configuration of the C2'-position is inconsequential but that O-methylation of this alcohol was deleterious to its mode of action. Additionally, the analog incorporating a mycosamine derivative from the enantiomeric series was devoid of activity.

Synthesis of Microcin SF608 through nucleophilic opening of an oxabicyclo[2.2.1]heptane

The total synthesis of Microcin SF608 is reported. Access to the octahydroindole core structure of Microcin SF608 relies on the TMSOTf/NEt(3)-mediated opening of an oxabicyclic ring system. Additional highlights of the synthetic strategy that is reported include a highly regioselective epoxide reduction and photolytic excision of a 3 degrees alcohol.