Unsaturated ketone moiety

Chalcones (including 11) contain a l,3-diaryl-a,/)-unsaturated ketone moiety and have anti-cancer properties [38]. As analogs of CA-4, 7, the mode of cytotoxic action of chalcones has been shown to be similar to the com-bretastatins. They bind to the colchicine site of tubulin and inhibit tubulin polymerization [39]. 

Reactions of unsymmetrical methylene 1,3-dicarbonyl compounds with enol ethers have been investigated by Yamauchi et al. [137]. As we have mentioned earlier, the a,/ -unsaturated ketone moiety in alkylidene-/ -ketoesters reacts exclusively as the oxabutadiene. However, high regioselectivity is also observed with mixed alkyl-phenyl-1,3-diketones with exclusive reaction of the aliphatic carbonyl group, whereas in alkylidene-1,3-dicarbonyl compounds bearing an aldehyde and a keto-moiety, the a,/J-unsaturated aldehyde reacts preferentially as oxabutadiene, but not exclusively [130a]. 

A homoveratryl enaminone derived from cyclohexane-1,2-dione was cyclized through a 1,4-addition at the a,/ -unsaturated ketone moiety of the enaminone319 (equation 237). The spiro compound obtained, which is a useful intermediate in the synthesis of erythrina-alkaloids, demonstrates the special character of a-ketoenamines. 

When the C—C bond is part of an a,p-unsaturated ketone moiety as in (38) (Scheme 8), direct (i.e. TT.ir excitation) triggers the ODPM reaction a stereoisomeric mixture of (39) and the 1,3-shift product (40) is formed in 93% and 6% yield, respectively, at 91% conversion of starting material. Compounds (40) and (39) are suggested to be generated from the singlet and triplet state, respectively. This finding... 

The Cope reairangement of 1,2-divinylcyclopropane systems in which one of the vinyl groups is part of an a,3-unsaturated ketone moiety has found considerable use in synthesis. A significant number of substrates have been prepared and subjected to thermal rearrangement and some of the products have been employed effectively for natural product syntheses. 

Chemoselective acetalization of an a,(3-unsaturated ketone moiety in the presence of a saturated keto group can also be achieved by using 2,4,6-collidinium / -toluenesulfonate (CPTS) as a catalyst. " ... 

Cyclobutane formation, occasionally in fairly low yield due to ring-opening reactions, also occurred by photochemical [2 - - 2] cycloaddition of vinylcyclopropane derivatives to an a, -unsaturated ketone moiety, " a cyclobuta-1,3-diene, a 1,4-benzoquinone, 2-acylthiophenes, and on irradiation of e t/o,enr/o-2,4-bis[( )-2-(methoxycarbonyl)vinyl]bi-cyclo[1.1.0]butane. A formal [2-1-2] cycloaddition also occurred on reaction of tricyclo[3.1.0.0 ]hex-3-ene with methyl 6-oxo-5-phenyl-l,3,4-oxadiazine-2-carboxylate to give methyl 9-oxo-10-phenyl-8-oxapentacyclo[4.4.0.0 ". 0 .0 °]decane-7-carboxylate, albeit in very low yield, after nitrogen extrusion. ... 

Under basic conditions, methanol added to methyl 2-(trimethylsiloxy)-2-vinylcyclopropane-carboxylate (15) via desilylation, ring opening and formation of an a,j6-unsaturated ketone moiety. 

Solasodenone, C27H41NO2, was isolated from roots or leaves of 5. hainanense. Structure (24a) was assigned to solasodenone on the basis of the following observations (a) the mass spectrum of the alkaloid showed the molecular ion at mje 411, and prominent fragment ions with mje 138 (base peak), 125, and 114, attributable to a spiro-amino-ketal, the presence of which was confirmed by the i.r. spectrum (b) the i.r. and u.v. spectra demonstrated the presence of an a -unsaturated ketone moiety (c) the o.r.d. curve and the chemical shifts of the C-18 and C-19 protons in the n.m.r. spectrum were consistent with a 3-oxo-A -cholestene skeleton (d) the n.m.r. spectrum also showed a singlet at 4.26 t and a... 

In a completely different context, an A-protected version of the amino acid cysteine has been found to be an excellent promoter for the intramolecular Rauhut-Currier reaction (Scheme 6.20)," in which an enolizable enone played the role of the Michael acceptor, adding to another a,p-unsaturated ketone moiety in already present at the substrate structure. The mechanism of the reaction involved the activation of the enone which has to play the role of the donor by the catalyst via sulfa-Michael addition through the mercapto functionality of the A-protected cysteine derivative. The formed enolate... 

In the first part of the chapter, we have covered mostly those reactions, initiated by Sjj2 type nucleophibc substitution, followed by a Michael reaction on a a,P-unsaturated ketone moiety, present in the intermediate adduct (S /Michael). A few examples of the reactions with carbonyl compounds and alkyl haHdes (twofold reactions) in the second step are also included. 

A series of ten withanolides, isolated from Physalis minima, were evaluated for their cytotoxic properties against HCT-116 and NCI-H460 cell lines. It was found that withaphysalin C (31) was active against both the cell lines [72]. The stmcture-activity relationship (SAR) studies of the C3dotoxic withanolides from Physalis minima and Physalis angulata indicate that the a,)S-unsaturated ketone moiety in ring A and 5jS-6/i oxirane moiety in ring B are important contributors in the cytotoxicity of withanolides. The absence of these two structural features may result in a loss or reduction of the cytotoxicity of withanohde [4]. 

Reddy, A.V.R., Subramanian, K., and Sainath, A.V.S., Photosensitive polymers synthesis, characterization and photocrosslinking properties of polymers with pendant a,P-unsaturated ketone moiety, J.Appl. Polym. Sci, 70, 2111, 1998. 

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