[reaction: see text] The facile stereoselective syntheses of endo-8-hydroxybicyclo[3.3.1]nonan-2-one and endo-7-hydroxybicyclo[3.2.1]octan-2-one, featuring an alpha-amino acid catalyzed intramolecular aldolization of sigma-symmetric substrates, are described. A high enantioselectivity and a high catalytic efficiency have been exhibited by (4R,2S)-tetrabutylammonium 4-TBDPSoxy-prolinate in the aldolization of 3-(4-oxocyclohexyl)propionaldehyde to give highly enantiomerically enriched (1S,5R,8R)-8-hydroxybicyclo[3.3.1]nonan-2-one.
(+)-Juvabione, a natural sesquiterpene exhibiting insect juvenile hormone activity, has been synthesized from sigma-symmetric 4-(2-formyl-ethyl)cyclohexanone by employing organocatalytic asymmetric aldolization and Norrish I-type fragmentation as the key steps.
[reaction: see text] A stereocontrolled synthesis of (-)-CP55,940, a potent cannabinoid receptor agonist, has been attained using a novel aldolization/retro-aldolization interconversion strategy, in which a temporarily generated chiral aldol motif plays essential roles.
Scheme 1. Reagents: a) Pb(OAc) 4 , Benzene (75z, 3a:3b=95:5); b) O 3 , MeOH, Then NaBH 4 , and Finally K 2 CO 3 (72z); c) HC(OMe) 3 , PPTS, THF; d) Ac 2 O, Then aq. NaOH (88z from 4); e) 6, DCC, DMAP, CH 2 Cl 2 (91z).Biosci. Biotechnol. Biochem., 67 (12), 2627-2631, 2003 Synthesis of the Sex Pheromone of the Citrus Mealybug, Pseudococcus cryptus The sex pheromone of the citrus mealybug (Pseudococcus cryptus ), [(1R,3R )-3-isopropenyl-2,2-dimethylcyclobutyl]methyl 3-methyl-3-butenoate, was synthesized from (+)-a-pinene inˆve operational steps in a 43z overall yield. The synthetic pheromone was identical with the natural pheromone in 1 H-NMR and mass spectroscopic properties, and showed almost the same pheromonal activity as the natural pheromone.
A sex pheromone component of Pseudococcus cryptus has been isolated and identified. The crude pheromone extract obtained by airborne collection was fractionated by liquid chromatography (LC) on Florisil, and further purified by high performance liquid chromatography and preparative Gas Chromatography (GC). The pheromone component was shown to be an ester, the alcohol part of which was identical to the known alcohol moiety of the pheromone of Planococcus citri. The chemical structure was determined to be 3-isopropenyl-2,2-dimethylcyclobutylmethyl 3-methyl-3-butenoate by MS and 1H NMR analyses. The absolute configuration of the pheromone was assigned as (1R,3R) by comparison of the retention time of the alcohol derived from the P. cryptus pheromone with those of the alcohol derived from P. citri pheromone, and a synthetic sample of alcohol enriched in the (1R,3R)-enantiomer, using a chiral GC stationary phase. The structure of the pheromone was confirmed by synthesis, and by bioassays in a glasshouse.
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