A synthetic methodology for the synthesis of 13,14-seco-steroids with substituents at C-14 and C-17 is described. The approach involves Grob fragmentation of 14β-hydroxy-17β-tosylates, ...hydroboration–oxidation of the intermediate Δ
13(17)-olefin, and hydride reduction of the 14-ketone. An unambiguous structural assignment of (13
R,14
S,17
S)-14,17-diacetoxy-3-methoxy-7α-methyl-13,14-secoestra-1,3,5(10)-triene was determined by X-ray analysis.
Optically active diols are one of the useful groups of compounds for asymmetric reaction as a chiral auxiliary or ligand. Among them, cyclic 1, 2-diols are characteristic of the restricted ...conformation. In this review, we wish to report the use of these compounds for the development of asymmetric reactions such as ring transformations based on intramolecular and intermolecular aldol reactions, and carba-spirocyclization, in which cyclic 1, 2-diols are added as a chiral source in combination with a Lewis acid. In addition, the synthesis of optically active cyclic diene compounds starting from cyclic 1, 2-diols is also discussed.
Quaternized γ‐amino alcohols 5 derived from ternary iminium salts 2 are stereospecifically converted into both unsaturated aldehydes/ketones 6 with a (Z)‐CC double bond in a Grob‐type fragmentation ...and highly functionalized oxetanes 7 by intramolecular substitution.
Ring transformation reaction seems to be one of the important strategies in synthetic chemistry, because it enables otherwise synthetically difficult targets to be accessible by ring transformation ...from other, readily prepared ring systems. Recently, a novel ring transformation based on aldol condensation followed by acetalization and subsequent Grob fragmentation has been developed by our group. This ring transformation using BF3 etherate/diol such as ethylene glycol seems to be widely applied for the synthesis. In this review, several reaction types of this ring transformation and its application to the synthesis of natural products having the unique skeleton are described.
Described here is a novel and simple route to the unsaturated hydroazulenones, bicyclo 5.3.0 dec-3-en-8-ones (12a, b), from photo-products, 7-acetoxytricyclo 5. 3. 0. 01, 5 decan-2-ones (2a, b).
A five step synthesis including highly regioselective intramolecular 2+2 photocycloaddition of 1-acetoxy-2-(hex-5-enoyl)-cyclopentene species leads to cis-and trans-fused bicyclo ...5.4.0-undec-3-en-8-one species in excellent stereocontrolled manner.
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