Stereoselective Total Synthesis of Polyrhacitides A and B

Prins cyclization: new strategy for the stereoselective total synthesis of Polyrhacitide A

A highly stereoselective total synthesis of polyrhacitide A, a polyketide natural product, has been accomplished by means of Prins cyclisation. The key precursor i.e. anti-1,3-diol for polyrhacitide A has been prepared from trans-2,6-disubstituted-3,4-dihydropyrans. In this approach, Prins cyclisation has successfully been utilised twice for the construction of 1,3-diol unit of polyrhacitide A. The key steps involved in this approach are Jacobsen hydrolytic kinetic resolution, Mitsunobu inversion, Prins cyclisation and Ring-closing metathesis (RCM).

Complex molecule synthesis by electrocatalytic decarboxylative cross-coupling

Modern retrosynthetic analysis in organic chemistry is based on the principle of polar relationships between functional groups to guide the design of synthetic routes1. This method, termed polar retrosynthetic analysis, assigns partial positive (electrophilic) or negative (nucleophilic) charges to constituent functional groups in complex molecules followed by disconnecting bonds between opposing charges2-4. Although this approach forms the basis of undergraduate curriculum in organic chemistry5 and strategic applications of most synthetic methods6, the implementation often requires a long list of ancillary considerations to mitigate chemoselectivity and oxidation state issues involving protecting groups and precise reaction choreography3,4,7. Here we report a radical-based Ni/Ag-electrocatalytic cross-coupling of substituted carboxylic acids, thereby enabling an intuitive and modular approach to accessing complex molecular architectures. This new method relies on a key silver additive that forms an active Ag nanoparticle-coated electrode surface8,9 in situ along with carefully chosen ligands that modulate the reactivity of Ni. Through judicious choice of conditions and ligands, the cross-couplings can be rendered highly diastereoselective. To demonstrate the simplifying power of these reactions, concise syntheses of 14 natural products and two medicinally relevant molecules were completed.

Stereoselective Total Synthesis of (-)-(2S,4R)-3'-Methoxyl Citreochlorol: Preparation and Use of New Proline-Based Auxiliary for Asymmetric Acetate Aldol Reaction

The first stereoselective total synthesis of (-)-(2S,4R)-3'-methoxy citreochlorol and (-)-(2S,4S)-3'-methoxy citreochlorol is demonstrated. A proline-based imidazolidinone was synthesized and used as chiral auxiliary for asymmetric acetate aldol reaction to generate initial chirality in the targeted molecule. Geminal dichloromethane functionality was introduced by the addition of in situ generated dichloromethyllithium to Weinreb's amide functional group.

Total Synthesis of Tetraketide and Cryptorigidifoliol I via a Sequential Allylation Strategy

A unified and efficient synthetic route for both tetraketide (1) and cryptorigidifoliol I (2) has been devised successfully from commercially available starting materials in 11 and 17 steps, with 16% and 11% overall yields, respectively. Highlights of the syntheses involved sequential Lewis acid-catalyzed highly regio- and diastereoselective allylations and intramolecular Mitsunobu lactonization.

A chiral phosphoric acid catalyst for asymmetric construction of 1,3-dioxanes

A chiral phosphoric acid catalyst enabled enantioselective 1,3-dioxane construction, useful for polyketide motif synthesis, via a hemiacetalization/intramolecular oxy-Michael addition cascade.