Synthesis of cyclic α-hydrazino acids

Duttagupta, Indranil; Goswami, Κ. N.; Sinha, Surajit

doi:10.1016/j.tet.2012.07.014

Cited by 21 publications

(10 citation statements)

References 33 publications

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“…Then, the hydrolysis of ester function, decarboxylation reaction, and hydrolysis of the trifluoroacetamide group were performed in one pot following our previously reported procedure . Accordingly, compounds 6a and 6b were treated with aqueous LiOH solution in THF (1:1) at 70 °C for 12 h. The crude products were directly reacted with Fmoc -OSu ester in standard conditions to isolate the Fmoc -protected amino acids 19a and 19b in 75 and 72% yields, respectively.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Protected 3,4- and 2,3-Dimercaptophenylalanines as Building Blocks for Fmoc-Peptide Synthesis and Incorporation of the 3,4-Analogue in a Decapeptide Using Solid-Phase Synthesis

et al. 2021

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Section: Resultsmentioning

confidence: 99%

Synthesis of Protected 3,4- and 2,3-Dimercaptophenylalanines as Building Blocks for Fmoc-Peptide Synthesis and Incorporation of the 3,4-Analogue in a Decapeptide Using Solid-Phase Synthesis

et al. 2021

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“…Surprisingly, TBAF was the only additive that initiated this unique rearrangement efficiently. It is known that TBAF can act as a strong base and is able to initiate amides and carbamates to undergo intramolecular cyclization. , Additionally, there have been a few reports of aryl migration of nosyl protecting groups accompanied by extrusion of sulfur dioxide under basic conditions. , In light of this known reactivity, we first reasoned that TBAF was acting as a base to initiate the reaction. The presence of the large nosyl group close to the enolizable proton may be preventing larger anions like chloride, bromide, and iodide from initiating the reaction.…”

Section: Resultsmentioning

confidence: 99%

“…It is known that TBAF can act as a strong base and is able to initiate amides and carbamates to undergo intramolecular cyclization. 16,17 Additionally, there have been a few reports of aryl migration of nosyl protecting groups accompanied by extrusion of sulfur dioxide under basic conditions. 18,19 In light of this known reactivity, we first reasoned that TBAF was acting as a base to initiate the reaction.…”

Section: ■ Introductionmentioning

confidence: 99%

Fluoride-Mediated Desulfonylative Intramolecular Cyclization to Fused and Bridged Bicyclic Compounds: A Complex Mechanism

2017

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We previously reported the synthesis of polysubstituted chiral oxazepanes in three steps from commercially available starting materials. The unexpected reaction of one of these 1,4-oxazepanes in the presence of TBAF provided a 4-oxa-1-azabicyclo[4.1.0]heptane core. This unusual process significantly increased the complexity of the molecular scaffold by introducing a bicyclic core. Surprisingly, the generated bicyclic structure featuring three stereocenters was a mixture of enantiomers with no other diastereomers observed. These striking experimental observations deserved further investigations. A combination of experimental and computational investigations unveiled a complex diastereoselective mechanism. Mechanistic rationale is presented for this observed rearrangement.

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“…The 1 H and 13 C NMR spectra matched with the literature data. 15 2-Allyl-2,3-dihydro-1H-inden-1-one (13b) and 2,2-Diallyl-2,3dihydro-1H-inden-1-one (14b) Following the general procedure gave 13b (353 mg, 39%) as a thick yellow liquid and 14b (297 mg, 26%) also as a thick yellow liquid. The 1 H and 13 C NMR spectra matched with the literature data.…”

Section: Diethyl 2-allylmalonate (13a) and Diethyl 22-diallylmalonatmentioning

confidence: 99%

Design and Synthesis of Angularly Annulated Spirocyclics via Enyne Metathesis and the Diels–Alder Reaction as Key Steps

2014

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We have developed a simple and an efficient route to a range of angularly fused spirocycles by the application of enyne metathesis and the Diels-Alder reaction as key steps. The enyne metathesis protocol has been further extended to the dibenzylation of indane-1,3-dione by using cross-enyne metathesis in the presence of hexa-1,5-diene with the aid of Grubbs' 1st generation catalyst followed by an aromatization sequence with DDQ.Since the development of ruthenium catalysts, 1 several metathesis protocols have opened up new and useful retrosynthetic strategies. 2 These advances have elevated organic synthesis to a higher level. The ring-closing enyne metathesis 3 (RCEM) protocol discovered by Katz in 1985 generate inner-outer 1,3-dienes, which are suitable for the Diels-Alder reaction. Generally, in the enyne metathesis sequence the alkylidene part migrates from the alkene to the alkyne carbon to deliver a conjugated diene and this skeletal reorganization is known as alkylidene migration reaction. Although ring-closing metathesis (RCM) is a useful route for the construction of carbon-carbon bonds, ring-closing enyne metathesis is unique and it is useful for the construction of conjugated 1,3-dienes containing polar functional groups in a single step. Over the last two decades, the metathesis sequence has been applied to generate challenging ring systems in natural products, 3k,4 in particular macrocyclic compounds and other biologically relevant substances. A number of selected bioactive natural products prepared by the enyne metathesis sequence are shown in Figure 1. 5 A simple access to dienes helps to expand the scope of the Diels-Alder reaction in preparative organic chemistry. It is worth noting that the DielsAlder reaction is a powerful tool that enhances molecular diversity immensely in a single step. Spirocyclics 2b,6 have attracted the attention of synthetic organic chemists because they constitute core structural units in several biologically important targets. 7 Molecules containing angularly fused aromatic systems with an extended π-framework are useful in designing electronic organic materials. These systems can create intricate molecular frameworks due to their unusual packing arrangement, which is difficult in linearly annulated structures. Although, a number of synthetic methods 8 are reported for the construction of linearly fused spirocyclics, only a limited number of strategies are available for the synthesis of angularly annulated spirocyclics. In our preliminary report, 9 we reported a simple synthetic strategy for the angularly annulation of indane-based spirocyclics starting with indane-1,3-dione (5) (Scheme 1, Figure 3). 10 Here, we report the full details of our preliminary work and also its extension to the generation of a library of angularly fused spirocyclics. We have assembled diverse spirocyclics by the sequential use of enyne metathesis and the Diels-Alder reaction which are atomeconomic. We have also expanded the metathesis sequence to a dibenzylated product by employing a crosseny...

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Synthesis of cyclic α-hydrazino acids

Cited by 21 publications

References 33 publications

Synthesis of Protected 3,4- and 2,3-Dimercaptophenylalanines as Building Blocks for Fmoc-Peptide Synthesis and Incorporation of the 3,4-Analogue in a Decapeptide Using Solid-Phase Synthesis

Synthesis of Protected 3,4- and 2,3-Dimercaptophenylalanines as Building Blocks for Fmoc-Peptide Synthesis and Incorporation of the 3,4-Analogue in a Decapeptide Using Solid-Phase Synthesis

Fluoride-Mediated Desulfonylative Intramolecular Cyclization to Fused and Bridged Bicyclic Compounds: A Complex Mechanism

Design and Synthesis of Angularly Annulated Spirocyclics via Enyne Metathesis and the Diels–Alder Reaction as Key Steps

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