Short intramolecular Diels-Alder approach to functionalized spiro[4.5]decanes

Nyström, Jan-E.; McCanna, Terrence D.; Helquist, Paul; Iyer, R. Subramonia

doi:10.1016/s0040-4039(00)98216-9

Cited by 26 publications

(7 citation statements)

References 39 publications

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“…90 mol % of HF and 10 mol % of pyridine) and would cleave the aziridine. However, when the HF−pyridine reagent was buffered with triethylamine, deprotection of 70a provided the desired alcohol 72a in 74% yield (88% based on recovered 70a ).…”

Section: Resultsmentioning

confidence: 99%

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

et al. 2003

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An enantiocontrolled route to aziridinomitosenes had been developed from l-serine methyl ester hydrochloride. The tetracyclic target ring system was assembled by an internal azomethine ylide cycloaddition reaction based on silver ion-assisted intramolecular oxazole alkylation and cyanide-induced ylide generation via a labile oxazoline intermediate (62 to 66). Other key steps include reductive detritylation of 26, methylation of the N-H aziridine 56, oxidation of the sensitive cyclohexenedione 68 to quinone 70, and carbamoylation using Fmoc-NCO. Although the aziridinomitosene tetracycle is sensitive, a range of protecting group manipulations and redox chemistry can be performed if suitable precautions are taken. A study of DNA alkylation by the first C-6,C-7-unsubstituted aziridinomitosene 11a has been carried out, and evidence for DNA cross-link formation involving nucleophilic addition to the quinone subunit is described.

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Section: Resultsmentioning

confidence: 99%

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

et al. 2003

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“…TBAF/AcOH, previously shown to be effective at removing TBS, generated only trace amounts of desired product (entry 14). HF·pyridine gave the desired product in 47% yield (entry 15), but HF·Et 3 N was inefficient even after 2 days of reaction (entry 16). NH 4 HF 2 /methanol/reflux gave the desired product in 52% isolated yield (entry 17).…”

Section: Results and Discussionmentioning

confidence: 99%

NH₄HF₂ as a Selective TBS-Removal Reagent for the Synthesis of Highly Functionalized Spiroketal via Tandem Deprotection/Spiroketalization Procedure

Zhang

Pan

et al. 2013

J. Org. Chem.

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NH4HF2 has been used for the first time to selectively remove the TBS protecting groups from diol ketone precursors in the synthesis of highly functionalized spiroketals. This method allows the synthesis of [5,6], [6,6], and [6,7] spiroketal skeletons, as well as benzannulated spiroketal with retention of acid-sensitive groups. In this way, spiroketals can be synthesized with diverse substituent groups in the skeleton or on side chains. To demonstrate the utility of this methodology, the diverse transformations of highly functionalized spiroketal 3f were also investigated.

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“…( R )-5-Phenylmethyl-1-propionyl-2-oxazolidinone, tetra- n -butylammonium azide, ethyl azidoformate, benzyl azidoformate, pyridinium dichromate, and HF·Et 3 N were prepared according to literature procedures. Other reagents were obtained commercially and were used as received.…”

Section: Methodsmentioning

confidence: 99%

Studies of Acyl Nitrene Insertions. A Stereocontrolled Route toward Lankacidin Antibiotics

1999

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Photochemically generated acyl nitrenes undergo facile addition to 4,5-dihydrofurans 20 and 24b to yield the novel 2-ethoxyoxazolines 21 and 25. The regiocontrolled C=C insertion has provided for introduction of the sterically hindered C-3 amido appendage of the lankacidins 1-4 with high stereoselectivity. High chemoselectivity for the C=C insertion pathway was demonstrated upon production of the acyl nitrene intermediate from azide 33b. Intramolecular competition for allylic C(3)-H insertion versus C=C addition yielded exclusive formation of seven-membered N-acyl aziridines 34a,b. The latent aldehydic functionality of oxazolines such as 21 and 25 is exposed upon a brief hydrolysis, permitting further chemical elaboration. Wittig condensation of the lactol from 25 has led to the synthesis of the lactone fragment 5, containing all of the necessary stereochemistry and functionality for incorporation into the lankacidin antibiotics. The acyl nitrene insertion into 4,5-dihydrofurans affords a route toward unusual beta-amido acids and amino sugar derivatives as shown via stereocontrolled formation of the amidofuranose derivatives 31 and 32. The three-step process of acyl nitrene addition, hydrolysis of the resulting 2,5-dialkoxy oxazoline intermediates, and Wittig carbon chain elongation provides the stereocontrolled formation of novel beta-amido esters.

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Short intramolecular Diels-Alder approach to functionalized spiro[4.5]decanes

Cited by 26 publications

References 39 publications

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

NH₄HF₂ as a Selective TBS-Removal Reagent for the Synthesis of Highly Functionalized Spiroketal via Tandem Deprotection/Spiroketalization Procedure

Studies of Acyl Nitrene Insertions. A Stereocontrolled Route toward Lankacidin Antibiotics

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Short intramolecular Diels-Alder approach to functionalized spiro[4.5]decanes

Cited by 26 publications

References 39 publications

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

Synthetic Enantiopure Aziridinomitosenes: Preparation, Reactivity, and DNA Alkylation Studies

NH4HF2 as a Selective TBS-Removal Reagent for the Synthesis of Highly Functionalized Spiroketal via Tandem Deprotection/Spiroketalization Procedure

Studies of Acyl Nitrene Insertions. A Stereocontrolled Route toward Lankacidin Antibiotics

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NH₄HF₂ as a Selective TBS-Removal Reagent for the Synthesis of Highly Functionalized Spiroketal via Tandem Deprotection/Spiroketalization Procedure