Total Synthesis of (+)-Cryptocaryol A Using a Prins Cyclization/Reductive Cleavage Sequence

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).

Stereoselective Synthesis of Euscapholide and Tetraketide via Prins Cyclisation and Ring-Closing Metathesis

A concise and diastereoselective total synthesis of tetraketide and euscapholide is described in ten steps in 10.6% overall yield from acetaldehyde and (S)-pent-4-ene-1,2-diol. Jacobsen hydrolytic kinetic­ resolution, Prins cyclization, ring-closing metathesis and oxa-Michael­ addition reactions are the key steps involved in the synthesis.

Bioinspired syntheses of cryptoflavanones C and D, oboflavanones A and B, and cryptoyunnanones G and H enabled by an acid-triggered cascade sequence

Collective total syntheses of oboflavanones A-B, cryptoflavanones C-D, and cryptoyunnanones G-H via a bioinspired acid-triggered olefin isomerization/hemiacetalization/dehydration/formal [3 + 3]-type cycloaddition cascade process are presented.

Feedstock Reagents in Metal-Catalyzed Carbonyl Reductive Coupling: Minimizing Preactivation for Efficiency in Target-Oriented Synthesis

Use of abundant feedstock pronucleophiles in catalytic carbonyl reductive coupling enhances efficiency in target-oriented synthesis. For such reactions, equally inexpensive reductants are desired or, ideally, corresponding hydrogen autotransfer processes may be enacted wherein alcohols serve dually as reductant and carbonyl proelectrophile. As described in this Minireview, these concepts allow reactions that traditionally require preformed organometallic reagents to be conducted catalytically in a byproduct-free manner from inexpensive π-unsaturated precursors.

The asymmetric syntheses of cryptocaryols A and B

The recent total syntheses of cryptocaryols A and B are reviewed. These efforts include the correction of the initially assigned absolute and relative stereochemistry of this class of natural products. In addition to enabling the initial structure activity relationships for this class of natural products, these syntheses demonstrated the practical utility of several novel synthetic approaches.

Versatile process for the stereodiverse construction of 1,3-polyols: iterative chain elongation with chiral building blocks

A versatile process for the construction of 1,3-polyols, a key structural element of polyketide-type natural products, is presented. The modular synthesis strategy involves the iterative chain elongation with novel four-carbon building blocks to access all possible stereoisomers of a growing 1,3-polyol chain. These chiral building blocks are designed to install four carbon atoms with two stereogenic centres by performing only four experimentally simple steps per elongation cycle, thus making these building blocks attractive for the realization of a universal platform from which to access a diverse range of polyketidic molecules.

Enantioselective Alcohol C-H Functionalization for Polyketide Construction: Unlocking Redox-Economy and Site-Selectivity for Ideal Chemical Synthesis

The development and application of stereoselective and site-selective catalytic methods that directly convert lower alcohols to higher alcohols are described. These processes merge the characteristics of transfer hydrogenation and carbonyl addition, exploiting alcohols and π-unsaturated reactants as redox pairs, which upon hydrogen transfer generate transient carbonyl-organometal pairs en route to products of C-C coupling. Unlike classical carbonyl additions, stoichiometric organometallic reagents and discrete alcohol-to-carbonyl redox reactions are not required. Additionally, due to a kinetic preference for primary alcohol dehydrogenation, the site-selective modification of glycols and higher polyols is possible, streamlining or eliminating use of protecting groups. The total syntheses of several iconic type I polyketide natural products were undertaken using these methods. In each case, the target compounds were prepared in significantly fewer steps than previously achieved.

Total Synthesis of Cryptocaryol A by Enantioselective Iridium-Catalyzed Alcohol C-H Allylation

The polyketide natural product cryptocaryol A is prepared in 8 steps via iridium catalyzed enantioselective diol double C-H allylation, which directly generates an acetate-based triketide stereodiad. In 4 previously reported total syntheses, 17-28 steps were required.

Substitution dependent stereoselective construction of bicyclic lactones and its application to the total synthesis of pyranopyran, tetraketide and polyrhacitide A

A novel strategy has been developed for the synthesis of bicyclic lactones and has been successfully applied to the total synthesis of pyranopyran, tetraketide, and polyrhacitide A.