A new general method for preparation of N-methoxy-N-methylamides. Application in direct conversion of an ester to a ketone

Williams, J. M.; Jobson, Ronald B.; Yasuda, Nobuyoshi; Marchesini, G.; Dolling, Ulf H.; Grabowski, Edward J. J.

doi:10.1016/0040-4039(95)01089-z

Cited by 161 publications

(198 citation statements)

References 16 publications

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“…Stubbornly, and despite prolonged investigation, this reaction would not go to completion although this was mitigated somewhat through the essentially quantitative recovery of unreacted starting material 95. Further transformation of 96 to the desired electrophile (99) was straightforward, involving deprotection by transesterification (97), methylation of the released alcohol (98) and, finally formation of the Weinreb amide [72] to conclude a second viable route to the C22-C28 fragment (Scheme 18).…”

Section: Synthesis Of Vinyl Bromide 69mentioning

confidence: 99%

Total Synthesis of Rapamycin

Ley

Tackett

Maddess

et al. 2009

Chemistry A European J

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For over 30 years, rapamycin has generated a sustained and intense interest from the scientific community as a result of its exceptional pharmacological properties and challenging structural features. In addition to its well known therapeutic value as a potent immunosuppressive agent, rapamycin and its derivatives have recently gained prominence for the treatment of a wide variety of other human malignancies. Herein we disclose full details of our extensive investigation into the synthesis of rapamycin that culminated in a new and convergent preparation featuring a macro-etherification/catechol-templating strategy for construction of the macrocyclic core of this natural product.

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Section: Synthesis Of Vinyl Bromide 69mentioning

confidence: 99%

Total Synthesis of Rapamycin

Ley

Tackett

Maddess

et al. 2009

Chemistry A European J

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“…Prior to the introduction of the furyl unit at C-12, carbonyl groups at C-4 and C-8 were transformed into bis-enol triflate 50 as scaffolds to introduce two ester groups at C-4 and C-8 by palladium-catalyzed carbonylation and at the same time to protect carbonyl groups at C-4 and C-8 in the next furyllithium addition. Prior to such synthetic sequences, the ester group at C-11 was transformed into Weinreb amide 51 quantitatively, 22 in which furyl unit was introduced by addition of 3-furyllithium to give furyl ketone 52.…”

Section: Synthesis Of Salvinorin a (1) : Second Generationmentioning

confidence: 99%

Highly Oxygenated Diterpenoids Associated to the Central Nervous System: Syntheses of Salvinorin and Forskolin

Hagiwara

Nozawa²

2009

J. Synth. Org. Chem. Jpn.

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Total synthesis of salvinorin A (1), a densely functionalized neoclerodane diterpenoid, having the most potent hallucinogenic activity and a selective k-opioid agonist, has been completed in 20 steps starting from enantiomerically-pure Wieland-Miescher ketone derivative 23. Subsequently, alternative total synthesis of salvinorin A (1) has been developed via palladium-catalyzed double carbonylation to bis-enol triflate followed by samarium diiodide-mediated double conjugate reduction in 13 steps. Forskolin (2), a highly oxygenated labdane diterpenoid and an activator of adenylate cyclase, has been synthesized in 12 steps and 12% overall yield from ptychantin A (62), which has been isolated from liverwort Ptychanthus striatus in sufficient yield. Tuning of the synthetic pathway enabled more expedient synthesis of forskolin (2) in 11 steps with 17% overall yield from ptychantins A (62) and B (63). In addition, synthesis of 1,9-dideoxyforskolin (3), an inhibitor of glucose transporter, has been accomplished in 8 steps and 37% overall yield from ptychantin A (62).

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“…The most important steps were the syn-selective aldol reaction between 14 and 15 and subsequent stereoselective reduction in order to construct four consecutive asymmetric centers to give 13. The hydroxy group of methyl (S)-3-hydroxy-2-methylpropionate (16a) was first protected with a 4-methoxybenzyl (MPM) group by treatment with MPM trichloroacetimidate, [7] and the resulting 17 was treated with N,Odimethylhydroxylamine to give a Weinreb amide, [8] which was readily converted into ethyl ketone 14 [9] without any racemization. Aldehyde 15 was next synthesized by a series of conventional reactions, starting from (R)-propionate 16b.…”

Section: Synthesis Ofmentioning

confidence: 99%