Cyclopentene-1,2-diones synthesis

Madindoline A 6 and B ent-7) are potent inhibitors of interleukin 6. In a total synthesis that also intended to determine relative and absolute configuration of these antibiotics, the densely functionalized cyclopentene-l,3-dione ring of 6 and 7 was elaborated via RCM of diene-diol 1 (Scheme 1). 

An important potential target of asymmetric hydrosilation catalysis is to the reduction of the cyclopenten-l,4-diones, 1, producing the 4-silyloxyeyclopentenones, 2, which are key intermediates in the synthesis of singleisomer prostaglandins (18-22). 

The BINAL-H reduction works well with alkenic - and alkynic ketones affording alcohols with satisfactory optical purities (Scheme It is noteworthy that (S)-BINAL-H [(S)-(28)] reduces 1-halo-l-octen-3-one and 2-cyclopentene-l,4-dione to give the corresponding carbinols, which are important chiral building blocks for the synthesis of prostaglandins by the conjugate addition approach. ... 

Two asymmetric synthesis approaches to chiral cyclopentenone derivatives can be envisaged. The first, reduced to practice by Noyori (43), involved reduction of cyclopentene-l,4-dione with lithium aluminum hydride chirally modified with binaphthol to give R-4-hydroxycyclopent-2-en-l-one in 94% e.e. Alternatively, manganese dioxide oxidation of allylic alcohol [40] (Fig. 7), in analogy to the cis isomer (54), would be expected to give the same enone. 

The de Mayo addition resxtion continues to be of considerable value for the formation of precursors for further synthesis. One example of this is the formation of the photoadducts (42, 43), prepared by photoaddition of isoprene to the enol of the dione ester (44), and have been used in a general synthesis of cyclopentenes. The photoadducts (42, 43) are produced in the standard fashion by the formation of a labile cyclobutane which subsequently ring opens. Takeshita et al. have reported the... 

Fomannosin (53), isolated from a wood-rotting fungus, has been synthesized in eleven steps from the cyclopentene (51) and the triester (52). ° Synthesis has been achieved from the dione (54) of an enzyme inhibitor called compactin (55), which has potential as a regulator of cholesterol bio-... 

Cyclopenten-l-ol, l,3-dimethyl-2-(7-methyl-3,7-tridecadien-ll-ynyl), , )-, 91-92, 279-280 2-Cyclopenten-1 -one, 3-methyl-2-(2-pentenyl)-, (Z)- (fasmone) synthesis, 29 2-Cyclopenten-l-ones syntheses by cyclizations from 1,4-dioxo compounds, 69, 79 from 5-nitro-l,3-diones, 81 Cyclophanes of porphyrins, 253 meta-Cyclophanes, 38, 338 pora-Cyciophanes = tricyclo[8.2.2.24,7]hexadeca-4,6,10,12,13,15-hexaenes synth., 38-39 Cyclopropane derivs. See Carbocycles, 3-membered... 

Cyclic enediynes. The realization that a number of antitumor antibiotics contain an enediyne core which is essential for their activity has led to extensive methods for synthesis of this ring system. One approach involves an aldol reaction with an acetylenic aldehyde protected as the Co2(CO)6 adduct. Thus the keto aldehyde 1, prepared in five conventional steps from cyclopentene-l,3-dione, on treatment with dibutylboron triflate and N(C2H5)y cyclizes to 2 in 69% yield. Attempted decomplexation with N-methyl-... 

Mikami [9] successfully utilized the Cu-phosphoramidite complex derived from chiral Bgand 8 and Cu(OTf)2 for the desymmetrization of cyclopentene-l,3-dione 9 (Scheme 11.3). The resulting enolates generated with dimethylzinc were efficiently trapped with butylaldehyde. Highly substituted cyclopentanedione 10 was formed with excellent diastereoselectivities and enantiomeric purities. This domino process was used for the formal synthesis of (+)-madindoline B (12) [10]. 

The Diels-Alder adduct of furan and maleic anhydride reacts with Grignard reagents to form lactones, which are converted to butenolides in a thermal cycloreversion reaction. Work continues on the synthesis of 4-ylidenebutenolides using the Wittig reaction on substituted maleic anhydrides the products have been converted into cyclopentene-l,3-diones. ... 

This strategy was used to synthesize spirocyclopenteneoxindoles, as well as stereodefined cyclopentenes. Likewise, Hu reported a [3 -f 2] annulation reaction of 2-atylideneindane-l,3-diones with MBH carbonates that proceeded smoothly in the presence of a multifunctional thiourea-phosphine catalysts to produce the corresponding quaternary carbon centered spirocyclic cyclopentenes. A phosphine-triggered tandem [3 + 4] annulation reaction between MBH carbonates and 1,4-diheteroatom dinucleophiles was described, which provided access to saturated seven-membered 1,4-heterocycles. Analogously, MBH carbonates were used as C3 synthons in asymmetric [3 + 2] annulation reactions for the asymmetric synthesis of 3-spirocyclopentene-2-oxindoles. Another kind of annulation reaction for the construction of highly functionalized stereodefined cyclopentene skeletons involved a Rauhut-Currier Domino Reaction. Finally, an efficient asymmetric [3 + 2] cycloaddition reaction between MBH carbonates of isatins and... 

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