A stereocontrolled route to both enantiomers of the necine base dihydroxyheliotridane via intramolecular 1,3-dipolar addition using the same chiral precursor

Hashimura, Kazuya; Tomita, Shun’ichi; Hiroya, Kou; Ogasawara, Kunio

doi:10.1039/c39950002291

Cited by 24 publications

(12 citation statements)

References 9 publications

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“…For the solid-phase synthesis of the b-hydroxy aldehydes 7 the chiral homoallylic alcohols 16-23 [25] and 15a and 15b [26] were synthesised following known procedures (Scheme 4). In addition, commercially available 3-buten-1-ol 14 and b-hydroxy esters 24a, 24b, 25a and 25b [27] were appropriate starting materials.…”

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confidence: 99%

Solid‐Phase Synthesis of [5.5]‐Spiroketals

2008

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An efficient and reliable multi-step synthesis of 251 natural product-like [5.5]-spiroketals on solid supports has been developed. As central key step, a double intramolecular hetero-Michael (DIHMA) reaction to alkynones was applied. The sequence allows for introduction of numerous substituents on the scaffold and for variation of stereochemistry. [5.5]-Spiroketals bearing an additional ketone were obtained in high overall yields. Further diversification was achieved by reduction of the ketone and reductive amination using polymer-supported borohydride, Grignard reaction and conversion to oxime derivatives in the solution phase.

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confidence: 99%

Solid‐Phase Synthesis of [5.5]‐Spiroketals

2008

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“…Alternatively, the unsaturated chain can be attached to a carbon of the aziridine ring. To illustrate that arrangement, we will examine the total synthesis of a necine base by Ogasawara depicted in Scheme 32 [81]. Aziridine 124 is prepared in two steps from benzyl-protected enantiopure glycidol and can undergo an intramolecular cycloaddition upon quick heating in refluxing diphenyl ether to give the bicyclic adduct 125 as the major isomer.…”

Section: Ring Expansions Of Nonactivated Aziridines and Azetidinesmentioning

confidence: 99%

Ring Expansions of Nonactivated Aziridines and Azetidines

Couty

David

2015

Topics in Heterocyclic Chemistry

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Ring expansions promoted by ring strain in aziridines and azetidines are reviewed in this chapter, putting emphasis on recent applications from the last decade. This vast subject cannot be surveyed here exhaustively, and the reader will be guided to relevant precedent reviews or key reports. Rather, special attention will be put on selected examples and their mechanistic details, aiming to demonstrate that high selectivity can be reached in these reactions. In this issue, this fastgrowing topic has been divided into two distinct chapters, this one dealing with "nonactivated" aziridines and azetidines. Therefore, the reader will only find here examples involving NH-or N-alkylaziridines and N-azetidines as substrates for ring expansions, while N-acyl, N-carbamoyl, or N-tosyl compounds, defined as "activated" substrates, will be presented in the next chapter. This distinction can appear quite arbitrary at first sight but is amply justified by the great difference in reactivity of these distinct substrates. The first part focuses on the ring expansions of nonactivated aziridines into up to seven-membered rings and is further divided into expansions involving the incorporation of one (or more) heteroatoms, followed by ring expansions involving only incorporation of carbon atoms. The same model is then followed for azetidines.

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“…Racemic pyrrolizidin-1-ones 131 and enantiopure dihydroxyheliotridane 132 were synthesized by utilizing in-tramolecular cyloadditions of C-alkenylazomethine ylides, whilst intramolecular cycloadditions of C-alkynylazomethine ylides have found application in a new synthetic route to the mitomycin skeleton (Scheme 22). 133 In the latter case, the desired azomethine ylide intermediates were generated in situ by cleavage of 5-alkynylsubstituted 2,3-trimethylene-oxazolium salts.…”

Section: Intramolecular Cycloadditions Of Azomethine Ylides and Münchmentioning

confidence: 99%