Polyene synthesis. Ready construction of retinol-carotene fragments, (.+-.)-6(E)-LTB3 leukotrienes, and corticrocin

Abstract

All products of the dirhodium tetraacetate catalyzed reactions of ethyl diazoacetate with furan, 2-methylfuran, 2,5-dimethylfuran, 2-ra-octylfuran, methyl furcate and methyl /3-(«-furyl)acrylate were isolated and characterized. They consist mostly of exo-cyclopropanecarboxylates and 1,4-diacyl-1,3-butadienes and some 3-(acylmethyl)furans. Treatment of the crude reaction mixtures with iodine or boron trifluoride furnishes 1,4-diacyl-1 (E) ,3 (E)-butadienes. Horner-Emmons condensation with the latter dicarbonyl compounds leads to l,6-diacyl-l,3,5-hexatrienes. Proper combinations of methyl -diazopropionate, furans, and -phosphono esters afford segments of retinol and /3-carotene, while combinations of -diazo ketones, furans, and «-phosphono ketones yield LTB3-like leukotrienes. Finally, dirhodium tetraacetate promoted decomposition of ethyl diazoacetate in l,2-bis(2-furyl)ethane and iodine treatment gives a diketo diester, whose reduction, dehydration, and hydrolysis leads to the naturally occurring dodecahexaenic dicarboxylic acid, corticrocin.

Enantioselective synthesis of (−)-paeonilide

“…36 As this scaffold is an interesting and very convenient gateway for natural product synthesis it was extensively utilized to enter a several natural product families (Scheme 9). 64 provided an access to the core nuclei of trans seven-membered sesquiterpenes 66 (Xanthanolides).…”

Synthesis of DEFG ring system of cneorins

“…The diazomalonates for the cyclopropanation reaction were synthesized as follows (Scheme 3 and Table 1). Alcohols 11-14 were treated with the monoester of malonic acid 15a-b in the presence of dicyclohexylcarbodiimide and DMAP 19 The ability of the furan ring to participate in carbenoid insertion reactions is well known, 22,23 and indeed, the model studies confirmed this. Whereas in a model study, the phenyl substituted diazomalonate 22 upon treatment with catalyst 10c produced the corresponding cyclopropanolactone in 67% yield, the 3-furyl substituted diazomalonates were extensively decomposed with this catalyst.…”

The Development of Ru(II) and Fe(II) Complexes for C-H and H2 Bond Activation

“…14 For perspective, the United States consumed ~27 trillion cubic feet of natural gas in 2014. 15 However, sources of natural gas are often situated in remote locations such as the Bakken oil field in North Dakota where there is no adequate natural gas transportation infrastructure, 16 making it difficult and expensive to move natural gas to places where it can be used. 2 Pipelines provide the means to exploit some of this natural gas but have not been utilized to their fullest potential due to the great expense (between $30,000 and $100,000 per inch-mile-for example, a 24 inch diameter pipeline at $100,000 per inch-mile costs $2,400,000 per mile-between 1993…”

“…15 Although it appeared that the major product from the deprotonation of 4 with NaHMDS was putative [C(pz) 4 ]Ru[P(OCH 2 ) 3 CEt](Cl)(4-chloroanilido) (7), the minor product was not identified. The reaction of 4 with LDA (lithium di(isopropyl)amide) (di(isopropyl)amine pK a = 40) 16 in THF-d 8 at -78 °C was performed; this reaction resulted in one new complex, the putative complex 7, that converted to a different complex overnight that was not identified or It would appear from these results that stronger bases such as LDA and NaH are necessary for clean deprotonation of 4.…”

“…[9][10][11][12][13][14][15][16][17][18] Reactions using furan can involve ring opening. For example, furan ring opening and hydrodeoxygenation of bioderived furan compounds to produce linear alkanes has been achieved in high yields and selectivity.…”