Lewis Base-Brønsted Acid-Enzyme Catalysis in Enantioselective Multistep One-Pot Syntheses.

Establishing one-pot, multi-step protocols combining different types of catalysts is one important goal for increasing efficiency in modern organic synthesis. In particular, the high potential of biocatalysts still needs to be harvested. Based on an in-depth mechanistic investigation of a new organocatalytic protocol employing two catalysts {1,4-diazabicyclo[2.2.2]octane (DABCO); benzoic acid (BzOH)}, a sequence was established providing starting materials for enzymatic refinement (ene reductase; alcohol dehydrogenase): A gram-scale access to a variety of enantiopure key building blocks for natural product syntheses was enabled utilizing up to six catalytic steps within the same reaction vessel.

Highly Enantioselective Allylation of Ketones: An Efficient Approach to All Stereoisomers of Tertiary Homoallylic Alcohols.

An optimized protecting group for allylboronates allowed the use of ketones in order to synthesize all isomers of quaternary homoallylic alcohols with high enantioselectivities. All symmetric isomers of the allylboronate were prepared in high yields and diastereoselectivities using Sn 2' reactions. The improved reactivity of the novel protecting group was verified by following the reaction kinetics with 1 H NMR spectroscopy. Mechanistic studies using DFT calculations were conducted to investigate the new findings. Thus, the stereochemical outcome and enhanced reactivity can be rationalized.