Application of a Radical Methodology toward the Synthesis of <i>d,l</i>-5α-Pregnanes and Related Steroids:  A Stereoselective Radical Cascade Approach

Zoretic, P. A.; Fang, Haiquan; Ribeiro, Anthony A.

doi:10.1021/jo980518+

Cited by 36 publications

(12 citation statements)

References 16 publications

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“…A list of the identified components is given in Table 1. Long-chain secondary alcohols (30) and the respective ketones were identified as reported earlier. [35] In addition, internal alkane-1,2-diols (31) were identified, accompanied by small amounts of the respective 1,3-and 1,4-diols.…”

Section: Resultsmentioning

confidence: 97%

“…(E)-Geranyl acetone (13) was then transformed into (E)-4,8-dimethyl-4,8-nonadienal (14) by the method described by Zoretic et al [30] This aldehyde was directly converted into the methyl ester 15 with PDC and methanol in DMF. [31] The following transesterification with Bu 2 SnO gave the precursor 16 for the final RCM by using the second generation Grubbs catalyst.…”

Section: Resultsmentioning

confidence: 99%

“…[31] PDC (9.34 g, 24.90 mmol) was added to a solution of aldehyde 14 [30] (690 mg, 4.15 mmol) in methanol (1 mL) and abs. DMF (21 mL) and stirred for 20 h under a nitrogen atmosphere.…”

Section: Gc-eadmentioning

confidence: 99%

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Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae

et al. 2009

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The small and large cabbage butterflies, Pieris rapae and P. brassicae, are found worldwide and are of considerable economic importance. The composition of the male scent-producing organs present on the wings was investigated. More than 120 components were identified, but only a small portion proved to be male specific. Major components were the known beetle pheromone ferrulactone (1) in P. rapae and its previously unknown larger analogue, brassicalactone (2), in P. brassicae. The latter carries an additional isoprene unit and is closely related to 1. Other components present in larger amounts on male relative to female wings were hexahydrofarnesylacetone (18) and phytol (23). Brassicalactone (2) was fully characterized by synthesis of its various diastereomers by using ring-closing metathesis. A similar approach to ferrulactone (1) failed, presumably because of its smaller ring size. Instead, this compound was synthesized by using a modified literature procedure. The biological activity of the compounds in the extract was tested by coupled gas chromatographic-electroantennographic (GC-EAD) analysis, which showed that both macrolides and the other major components of the wings can be detected by the antennae of the conspecific female butterflies. Other detectable compounds included several alkanes, which are typical constituents of the butterfly cuticula, derivatives of phytol (23) and long-chain secondary alcohols. Finally, bioassays with males showed that the mixture of 1 (P. rapae) or 2 (P. brassicae) together with 18 and 23 applied to freshly eclosed males increased mating success compared to untreated males. Therefore, the two macrolides 1 and 2 are aphrodisiac pheromone components of male small and large cabbage white butterflies, respectively.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

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Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae

et al. 2009

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“…[43] In view of these results, we explored the possibility of using dissolving metal conditions on the analogous nitrile 29, which could be expected to result in decyanation (Scheme 5). [44,45] The added attraction of this procedure was the prospect of combining the removal of the superfluous substituent with a Birch reduction of the aromatic ring.…”

Section: Resultsmentioning

confidence: 99%

“…After this time the solution was extracted with ethyl acetate, the organic layers were combined and washed with water and brine, and then dried and evaporated under vacuum to give the crude diketone which was purified by column chromatography (ethyl acetate/petroleum spirit, 1/1) to give the pure diketone 44 (37 mg, 45%) as an oil. (4aSR,6aSR,7SR,13RS,13aRS,13bRS)-2,3,4,4a,5,6,6a,7, 12,13,13a,13b-Dodecahydro-5,7-dihydroxy-10-methyl-7, 13-methano-1H-naphtho [2 ,1 :4,5]cyclohepta [1,2-b] pyridine (45) Diketone 44 (10 mg, 0.024 mmol) was dissolved in ethanol (3 mL) and H 2 NOH•HCl (5 mg, 0.072 mmol) was added. The resulting solution was heated under reflux overnight and then diluted with NaOH solution (1 M, 10 mL) and extracted with EtOAc.…”

Section: Conversion Of the βγ-Enone-dimethoxy Acetal 40 Into The αβmentioning

confidence: 99%

The Total Synthesis of the Galbulimima Alkaloid GB 13

Mander

McLachlan

2003

J. Am. Chem. Soc.

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This contribution describes a synthetic approach to alkaloid GB 13, previously isolated from the North Australian and Papua New Guinean rain forest tree Galbulimima belgraveana. A Birch reductive alkylation of 2,5-dimethoxybenzoic acid by 3-methoxybenzyl bromide, followed by an acid-catalyzed cyclization was used to synthesize the [3.3.1]bicyclononane 8. A ring contraction performed on the diazo derivative 9 of the [3.3.1]bicyclononane led to [3.2.1]bicyclooctane 10. This [3.2.1]bicyclooctane was converted into a dienophile and subjected to a Diels-Alder reaction to generate a pentacyclic intermediate 13 with a carbon skeleton closely resembling the target alkaloid. The surplus substituent, required for activation and regioselectivity in the Diels-Alder reaction, was removed using Birch reductive conditions to effect a decyanation. It was discovered that a Birch reduction of the aromatic ring also present in the molecule could be performed at the same time to give the enone 15, which was cleaved by means of an Eschenmoser fragmentation. The piperidine ring found in the natural product was formed by reductive cyclization of the bis-oxime 18 derived from the alkynyl ketone 17 and the resulting material further elaborated to GB 13 (1) via ketone 20.

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The Krapcho Dealkoxycarbonylation Reaction of Esters with α‐Electron‐Withdrawing Substituents

Krapcho

Ciganek

2013

Organic Reactions

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The Krapcho reaction involves esters with α‐electron‐withdrawing substituents such as malonates, β‐keto esters, and α‐cyano esters, which undergo dealkoxycarbonylation on being heated in polar aprotic solvents (such as DMSO, DMF, or HMPT) in the presence of water, or in polar aprotic solvents with water in the presence of added salts (such as NaCN, NaCl, LiCl, LiI, or MgCl 2 ). This procedure avoids the use of strongly aqueous acidic and alkaline conditions and tolerates many functional and protecting groups. The chapter presents the mechanistic aspects of this procedure, which include reaction parameters such as solvents, salts, other additives, and the use of microwave irradiation. The diastereoselectivity of protonation of the enolate intermediate leading to the dealkoxycarbonylated products is discussed. Trapping of the intermediate enolate by electrophiles other than a proton is illustrated. Potential side reactions and same‐pot subsequent reactions of substrates are discussed along with functional‐group compatibility for halogens and nitrogen, oxygen, sulfur, selenium, and carbon functional groups. Several examples of applications of this methodology for the synthesis of natural products along with experimental conditions and procedures are presented. Closely related methods are discussed in the Comparison with Other Methods section. The tables, which consist of 371 pages, are grouped according to substrate structure. Selective entries for other methods (excluding classical aqueous acidic or basic methods) are included in the tabular survey for comparative purposes.

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Application of a Radical Methodology toward the Synthesis of d,l-5α-Pregnanes and Related Steroids: A Stereoselective Radical Cascade Approach

Cited by 36 publications

References 16 publications

Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae

Aphrodisiac Pheromones from the Wings of the Small Cabbage White and Large Cabbage White Butterflies, Pieris rapae and Pieris brassicae

The Total Synthesis of the Galbulimima Alkaloid GB 13

The Krapcho Dealkoxycarbonylation Reaction of Esters with α‐Electron‐Withdrawing Substituents

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