Facial Selective Photoreduction of Steroids:  Role of Zeolites

Rao, V. Jayathirtha; Uppili, Sundara Rajan; Corbin, David R.; Schwarz, Stephan; Lustig, Steven R.; Ramamurthy, V.

doi:10.1021/ja972976q

Cited by 28 publications

(15 citation statements)

References 18 publications

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“…By contrast to the small pore zeolites A and ZSM-5, we anticipated complete adsorption (confinement) of epoxy polyene terpenes possessing up to 30 carbon atoms (triterpenes) within NaY supercages, as it well known that the faujasite cavities can host even steroids. [21] Initially, the cyclization of the small acyclic terpenoids 3, 5a-d and 10a, b shown in Table 1 was examined. [22] The reactions were carried out by adding a hexane solution containing a suitable amount of the epoxy terpenoid (see discussion below) to the dry NaY, and the resulting slurry was left reacting for a certain period of time (Table 1).…”

Section: Cyclization Of Small Epoxy Terpenoidsmentioning

confidence: 99%

Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols

et al. 2008

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A variety of epoxy polyene terpenes cyclize readily by confinement within zeolite NaY to form primarily products of monocyclization. The monocyclization pathway is highly predominant, irrespectively of the side chain of the epoxy terpene, while the monocyclic products possess regioselectively an exomethylenic double bond. The selective monocyclization in the case of epoxyfarnesyl acetate, epoxyfarnesylacetone or 2,3-epoxysqualene, provides a direct route to the synthesis of a variety of natural products, such as elengasidiol, farnesiferols B-D, achilleol A, camelliol C and to four farnesylacetonederived metabolites isolated from the brown algae Cystophora monoliformis. The optical rotation of achilleol A derived from the cyclization of (S)-2,3-epoxysqualene matches with that of the natural product, thus the absolute configuration of achilleol A was established as 1S,3R. From the mechanistic point of view, the NaY-promoted cyclization of 9,10-epoxygeranylacetone, selectively deuterium labelled at the C-10 methyl group, is > 97% stereoselective with respect to the topicity of the gem-dimethyl group. This result is in agreement with a concerted mechanism. Finally, we have proved through labelling experiments, for the first time, that the biomimetic transformation of epoxy polyene terpenes to 2,3,4-trimethylcyclohexanones upon acid catalysis is a highly stereoselective process. Thus, the less hindered gem-methyl group on the epoxide functionality becomes a-to the carbonyl in the final isomerized product.

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Section: Cyclization Of Small Epoxy Terpenoidsmentioning

confidence: 99%

Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols

et al. 2008

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“…Unexpectedly, the photoreaction with NaY zeolite in hexane lead to a dramatic inversion of the diastereoselectivity to give 21a and 21b in 85% and 80% yield, respectively. 54 As illustrated in Scheme 4.10 , the diastereomeric cyclobutanols generated by the Norrish -Yang type II reaction of adamantly ketoesters 23 are readily converted to the corresponding δ -ketoesters 24 via retro -aldol reaction. The δ -ketoesters 24 are given in 4 -22% de upon photolysis of 23 in isotropic solution of hexane and acetonitrile.…”

Section: Diastereodifferentiating Photoreactions With Achiral Zeolitementioning

confidence: 99%

Supramolecular Photochirogenesis

Yang¹,

Inoue²

2011

Supramolecular Photochemistry

132

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“…21 Upon irradiation of alicyclic enones within zeolites, a most remarkable consequence of alkali metal ion -controlled state switching can be seen in the photoproduct distributions. 22,23 Steroidal enones such as cholesteryl acetate ( 11 ) yield product 13 from n π * triplet state in solution (Scheme 10.4 ). However, within NaY zeolite, the major product 12 is derived from the π π * triplet state.…”

Section: Switching Of Electronic Confi Guration (N π * -π π * Switching)mentioning

confidence: 99%

Controlling Photoreactions Through Noncovalent Interactions Within Zeolite Nanocages

Ramamurthy¹,

Sivaguru²

2011

Supramolecular Photochemistry

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Drawing inspiration from nature, chemists have employed confi nement as a tool to achieve selectivity in chemical reactions. 1 Confi ning reactants has the power to drive chemical reactions with astonishing precision as seen in the remarkable selectivities exhibited by enzymes in chemical processes, the phenomenon of photosynthesis, and so on. Within a confi ned environment, 2 the familiar electronic and steric effects of solution chemistry are replaced by structural and topological factors that frequently result in products that display a level of selectivity or specifi city that has hitherto been unobtainable in solution. Upon confi nement, inherent reactivity of confi ned guests often becomes of secondary importance compared with features such as symmetry, geometric considerations, and noncovalent interactions that develop within the confi ned environments. This review will highlight the confi nement effect offered by zeolite Y supercages, 3,4 the noncovalent interaction (viz., cation -π and cationcarbonyl interactions) 5,6 that develops upon inclusion of substrates within faujasite zeolite X/Y supercages, and the effect of such interactions in photophysical and photochemical processes). 7,8 ZEOLITE Y SUPERCAGES: NANOCAVITY THAT OFFERS NONCOVALENT INTERACTIONSZeolites 3 are inorganic crystalline aluminosilicate microporous materials (particle size ranges 0.1 -10 μ m, 40 naturally occurring and more than 100 synthetic 389Supramolecular Photochemistry: Controlling Photochemical Processes, First Edition. Edited by V. Ramamurthy and Yoshihisa Inoue.

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Facial Selective Photoreduction of Steroids: Role of Zeolites

Cited by 28 publications

References 18 publications

Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols

Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols

Supramolecular Photochirogenesis

Controlling Photoreactions Through Noncovalent Interactions Within Zeolite Nanocages

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