Electrophilic Cyclization of 1,6‐Dienes Containing an Allylsilane Moiety − Enantioselective Synthesis of <i>cis</i>‐ and <i>trans</i>‐γ‐Irone

Beszant, Stephen; Giannini, Elios; Zanoni, Giuseppe; Vidari, Giovanni

doi:10.1002/ejoc.200300276

Cited by 18 publications

(25 citation statements)

References 53 publications

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“…As part of a program of synthesis of enantiomer-enriched norterpenoid odorants and their olfactory evaluation, we have previously described the stereoselective preparation of ionones [5] and irones [6]. In the present work, we have focused our attention on the three C(13)-alkyl-substituted a-ionone homologues 8 -10, aiming at investigating the relationship between olfactory properties and the steric bulk of the substituents on the cyclohexene C¼C bond.…”

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confidence: 99%

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

Luparia

Boschetti

Piccinini

et al. 2008

Chemistry & Biodiversity

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To study the influence of the steric bulk of the substituents at C(5) on the olfactory characteristics of alpha-ionone, the (S)-antipodes of compounds 8-10 were synthesized starting from (S)-alpha-cyclogeraniol (14a). The latter was available in useful preparative yield with 95% ee by enantioselective lipase-PS-mediated acetylation of the racemic mixture. Key step in the conversion of 14a to 8-10 was an S(N)2'-type reaction of an organocuprate on the allylic phosphate 20, which appears to be a general method for the introduction of an alkyl substituent at the cyclohexene C=C bond of ionones. Olfactory evaluation showed that, compared to the parent (S)-alpha-ionone (1), the odor strength and fragrance facets of the three analogues 8-10 are significantly influenced by the bulkiness of the substituent at C(13), giving further evidence that hydrophobic interactions of this group play a significant role in the chemoreception of ionones. In particular, the odor of the ethyl derivative 8 was found to be significantly stronger than that of the parent (S)-alpha-ionone (1).

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confidence: 99%

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

Luparia

Boschetti

Piccinini

et al. 2008

Chemistry & Biodiversity

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“…In parallel experiments, cyclization of 63 with Hg(OCOCF 3 ) 2 was investigated [50]. As expected, the reaction proceeded with no racemization at C-6 and produced an almost equimolecular mixture of cis-and trans-67.…”

Section: Biomimetic Cyclizations Of Differently Substituted Acyclic Smentioning

confidence: 78%

“…Cyclization of diene 62 with Hg(OCOCF 3 ) 2 (1.05 equiv) in propionitrile at -40°C proceeded under a much higher diastereocontrol, affording a 7:1 mixture of cis-and trans-67 [50]. This remarkable result can be explained by assuming that the reaction was highly concerted and was promoted by an antiperiplanar attack of the 2 -double bond on bridged mercuric ion 68 (Fig.…”

Section: Biomimetic Cyclizations Of Differently Substituted Acyclic Smentioning

confidence: 96%

“…In a related study, we investigated the intramolecular cyclizations of trimethylsilyl-substituted (E)-1,5-diene 62 and (E)-1,6-diene 63 in an approach towards the core structure 67 of -cis- (45) and -trans-irone (46) [50] (Scheme 25). Cyclization of 62 or 63 with SnCl 4 (4 equiv) in wet CH 2 Cl 2 at -30/-20°C afforded a mixture of stereoisomers cis-/trans-67.…”

Section: Biomimetic Cyclizations Of Differently Substituted Acyclic Smentioning

confidence: 99%

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Biomimetic Cyclizations of Functionalized Isoprenoid Polyenes: A Cornucopia of Synthetic Opportunities

Brunoldi¹,

Luparia²,

Porta³

et al. 2006

COC

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The synthetic aspects of biomimetic cyclizations of isoprenoid polyenes, simulating one of the key steps in the biosynthesis of terpenoids in living organisms, have been reviewed, with emphasis on transformations carried out on carbocyclic systems. These reactions are made possible by a clever choice of initiating and terminating units of cyclization, and by introducing suitable functional groups on the acyclic precursor which can be manipulated after cyclization. Complex functionalized polycyclic structures are thus assembled with an efficiency paralleling or even superior that of purely biochemical processes. In particular, synthetic strategies towards alkyl and hydroxyl-substituted compounds have been examined in detail. The last part of the review has been dedicated to a thorough illustration of carbenium ion initiated polyene cyclizations, with their synthetic applications and a discussion of the different mechanisms proposed.

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“…Grignard reaction of 20 with 3.0 equivalents of MeMgBr in Et 2 O gave 21 in quantitative yield. Compound 21 reacted with TsCl and pyridine in CH 2 Cl 2 to form tosylate 22 in 85% yield [17]. Nucleophilic substitution of 22 with NaI in acetone gave 23 in 77% yield.…”

Section: Figurementioning

confidence: 99%

New approach to paricalcitol synthesis

Yue

Xue

et al. 2012

Chin. Sci. Bull.

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Paricalcitol, an analog of vitamin D, is used as a drug for the prevention and treatment of secondary hyperparathyroidism. In this paper, a new strategy for the synthesis of paricalcitol is described. This approach includes three main improvements: one-pot regioselective ozonization cleavage of the side-chain and methylene at C-19, free-radical reduction removal of the OH group formed at C-19, and side-chain assembly using a Wittig reaction. These are all new strategies for the synthesis of 19-nor-vitamin D 2 compounds. cleavage of the methylene group on ring A of vitamin D 2 were achieved by ozonization/Julia olefination and dihydroxylation/oxidation with NaIO 4 , respectively.Large-scale, efficient, convenient synthesis of paricalcitol is still a challenge. We therefore tried to find an efficient synthetic method. First, we tried to improve the main conversion steps, especially removal of the C-19 methylene group and assembly of the side-chain. It was found that the side-chain and C-19 methylene can be cleaved selectively in

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Electrophilic Cyclization of 1,6‐Dienes Containing an Allylsilane Moiety − Enantioselective Synthesis of cis‐ and trans‐γ‐Irone

Cited by 18 publications

References 53 publications

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

Biomimetic Cyclizations of Functionalized Isoprenoid Polyenes: A Cornucopia of Synthetic Opportunities

New approach to paricalcitol synthesis

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