Here, we have demonstrated that the presence of a carbonyl group at C7 position prevents the olefin metathesis of endo-norbornene derivatives due to complexation of the metal alkylidene. Time-dependent NMR studies showed the presence of new proton signals in the metal alkylidene region, which indicate the formation of metal complex with the carbonyl group of the substrate. These observations were further proved by ESI-MS analysis. Whereas computational studies showed that the catalyst was interacting with the C7 carbonyl group and aligned perpendicular to that of norbornene olefin. These endo-keto norbornene derivatives were reduced to hydroxyl derivatives dia­stereoselectively. Ring-rearrangement metathesis (RRM) of these hydroxyl derivatives, produced the [6/5/6], and [5/6/5] carbo-tricyclic cores of natural products in one step. Whereas the RRM of O-allyl derivatives, delivered the oxa-tricyclic compounds in a single step with excellent yields.

The synthesis of propellanes containing bicyclo[2.2.2]octene via olefin metathesis approach is less explored.Herein, we describe a simple and convenient method to synthesize propellane derivatives containing a bicyclo[2.2.2]octene unit which are structurally similar to 11b-HSD1 inhibitors by sequential usage of the Diels-Alder reaction, C-allylation and ring-closing metathesis (RCM) as the key steps. Additionally, we expanded this approach to an endo-tricyclo[4.2.2.0 2,5 ]decene derivative which is a useful monomer for polymer synthesis and we have also synthesized basketene and anthracene-based propellanes using the same strategy.

A concise synthetic approach to [5/5/6] tricyclic pyrrolidine core of dendrobine is reported. This methodology relies on the construction of β-hydroxylactams by NaBH4-I2 reduction followed by reaction of allylsilane with the aid of Lewis acid to generate alkenyl lactams in good yields. Further, ring-opening metathesis (ROM) followed by ring-closing metathesis (RCM) were used to assemble the [5/5/6] aza-tricyclic skeleton of dendrobine. This short synthetic route has been expanded to assemble tricyclic [5/5/8] system with pentenylboronic acid.

Cyclic phosphatidic acids (cPAs) are bioactive compounds with therapuetic potential, but are in short supply. We describe a robust synthesis of cPAs employing an efficient cyclophosphorylation procedure and report on...

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