5-epi-Incensole: synthesis, X-ray crystal structure and absolute configuration by means of ECD and VCD studies in solution and solid state

Incensole 1 and its acetate 2, found in incense, demonstrate interesting biological activities. Incensole acetate 2 was prepared on a large scale by employing the Paul and Jauch protocol from the crude extracts of Boswellia papyrifera Hochst. 5-epi-Incensole 3, obtained as colorless crystals, was prepared from incensole acetate via three steps; deacetylation, oxidation and reduction. The structure of 5-epi-incensole 3 was elucidated by means of spectroscopic data analysis, and the absolute configuration was established by single crystal X-ray analysis in combination with electronic and vibrational circular dichroism. In particular, the applicability of the solid-state ECD/TDDFT protocol to a compound with only two non-conjugated alkene chromophores was verified

The ancient CYP716 family is a major contributor to the diversification of eudicot triterpenoid biosynthesis

Triterpenoids are widespread bioactive plant defence compounds with potential use as pharmaceuticals, pesticides and other high-value products. Enzymes belonging to the cytochrome P450 family have an essential role in creating the immense structural diversity of triterpenoids across the plant kingdom. However, for many triterpenoid oxidation reactions, the corresponding enzyme remains unknown. Here we characterize CYP716 enzymes from different medicinal plant species by heterologous expression in engineered yeasts and report ten hitherto unreported triterpenoid oxidation activities, including a cyclization reaction, leading to a triterpenoid lactone. Kingdom-wide phylogenetic analysis of over 400 CYP716s from over 200 plant species reveals details of their evolution and suggests that in eudicots the CYP716s evolved specifically towards triterpenoid biosynthesis. Our findings underscore the great potential of CYP716s as a source for generating triterpenoid structural diversity and expand the toolbox available for synthetic biology programmes for sustainable production of bioactive plant triterpenoids

A simple and efficient new synthesis of vicinal diols by reductive coupling of carbonyl compounds

A universally applicable, new 'pinacolic reduction' for aldehydes and ketones is described

Efficient, low temperature Reformatsky reactions of extended scope

Laminated zinc/silver–graphite reacts rapidly at low temperatures with α-bromo- and α-chloro-alkanoates and cyclic ketones allowing high yielding and even stereospecific Reformatsky reactions

SYNTHESIS AND REARRANGEMENT REACTIONS OF C-ALKYLIDENE CARBOHYDRATES

Direct: olefinations on one hand in comparison to eliminations of aldols cf various uloses on the other each proved to be specific as to the sice of unsaturation in the branched-chain products, found to be interconvertible with one exception under a variety of conditions. Although shown to be generally equivalent to its Witcig-counterpart:, the Peterson reagent employed is liable to cause eliminations in the initial olefin. One of the branched-chain products appears to be of unusual molecular rigidity as evidenced by a large 5J coupling

Magnesium- and Titanium-induced Reductive Coupling of Carbonyl Compounds: Efficient Syntheses of Pinacols and Alkenes

Finely dispersed magnesium on graphite was found to be a totally selective single-electron transfer reagent of general utility for the redn. of various kinds of carbonyl and dicarbonyl compds. to pinacols, a reaction quite compatible with a no. of functional groups. Similarly, titanium on graphite proved to be a universally applicable reducing agent for the efficient conversion of pinacols, carbonyl and dicarbonyl compds. into alkenes and cycloalkenes resp. and for the cyclization of oxo alkanoates to enol ethers, facilitating and unifying the highly useful McMurry reaction. The practicability of the presently known carbonyl coupling methods is discussed in the light of these results