Asymmetric Allylation Catalyzed by Chiral Phosphoric Acids: Stereoselective Synthesis of Tertiary Alcohols and a Reagent-Based Switch in Stereopreference.

The substrate scope of the asymmetric allylation with zinc organyls catalyzed by 3,3-bis(2,4,6-triisopropylphenyl)-1,1-binaphthyl-2,2-diyl hydrogenphosphate (TRIP) has been extended to non-cyclic ester organozinc reagents and ketones. Tertiary chiral alcohols are obtained with ee's up to 94% and two stereogenic centers can be created. Compared to the previous lactone reagent the stereopreference switches almost completely, proving the fact that the nature of the organometallic compound is of immense importance for the asymmetry of the product.

Oxygen-Free Regioselective Biocatalytic Demethylation of Methyl-phenyl Ethers via Methyltransfer Employing Veratrol--demethylase.

The cleavage of aryl methyl ethers is a common reaction in chemistry requiring rather harsh conditions; consequently, it is prone to undesired reactions and lacks regioselectivity. Nevertheless, -demethylation of aryl methyl ethers is a tool to valorize natural and pharmaceutical compounds by deprotecting reactive hydroxyl moieties. Various oxidative enzymes are known to catalyze this reaction at the expense of molecular oxygen, which may lead in the case of phenols/catechols to undesired side reactions (e.

Mechanistic Studies of the TRIP-Catalyzed Allylation with Organozinc Reagents.

3,3-Bis(2,4,6-triisopropylphenyl)-1,1-binaphthyl-2,2-diyl hydrogenphosphate (TRIP) catalyzes the asymmetric allylation of aldehydes with organozinc compounds, leading to highly valuable structural motifs, like precursors to lignan natural products. Our previously reported mechanistic proposal relies on two reaction intermediates and requires further investigation to really understand the mode of action and the origins of stereoselectivity. Detailed ab initio calculations, supported by experimental data, render a substantially different mode of action to the allyl boronate congener.

TRIP-Catalyzed Asymmetric Synthesis of (+)-Yatein, (-)-α-Conidendrin, (+)-Isostegane, and (+)-Neoisostegane.

The asymmetric allylation under the assistance of catalytic amounts of 3,3'-bis(2,4,6-triisopropylphenyl)-1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (TRIP) allows the concise construction of the lignan scaffold from simple aldehydes and allylic bromides with full control of the two formed stereocenters. This young methodology has been employed to synthesize four naturally and pharmaceutically active lignans. Members of the dibenzylbutyrolactone, the tetraline, and the dibenzocyclooctadiene classes have been synthesized in 40-47% overall yield along four-step synthetic routes.

Chemoenzymatic Total Synthesis of Deoxy-, epi-, and Podophyllotoxin and a Biocatalytic Kinetic Resolution of Dibenzylbutyrolactones.

Podophyllotoxin is probably the most prominent representative of lignan natural products. Deoxy-, epi-, and podophyllotoxin, which are all precursors to frequently used chemotherapeutic agents, were prepared by a stereodivergent biotransformation and a biocatalytic kinetic resolution of the corresponding dibenzylbutyrolactones with the same 2-oxoglutarate-dependent dioxygenase. The reaction can be conducted on 2 g scale, and the enzyme allows tailoring of the initial, "natural" structure and thus transforms various non-natural derivatives.