Unexpected bromination reaction of isosteviol methyl ester with bromoalkanes

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

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“…The reaction of isosteviol methyl ester with 1,2-dibromoethane produced 15-bromoisosteviol methyl ester in 92% yield …”

Section: Bromination Reactionsmentioning

confidence: 99%

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

2016

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“…Bromination at the α‐position relative to the carbonyl of 3 can be achieved by treatment with an excess of bromoethane/DMSO under basic conditions 14. The depicted stereochemistry is based on analogous transformations 15. Surprisingly, the reduction of brominated substrate 6a with sodium borohydride again leads to the formation of debrominated alcohol 5 14.…”

Section: Chemical Transformationsmentioning

confidence: 92%

(–)‐Isosteviol as a Versatile Ex‐Chiral‐Pool Building Block for Organic Chemistry

2013

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(–)‐Isosteviol is readily available in large quantities by the acidic treatment of a common alternative sweetener. The two functional groups of (–)‐isosteviol are presented on the same side of the ent‐beyerane scaffold with a mutual C–C distance of about 7 Å. Their unique concave arrangement experiences a strong asymmetric environment due to an adjacent methyl group. Consequently, this building block has found several applications in supramolecular chemistry and organocatalysis. These areas and the chemical modification of this scaffold as well as its biological activity are surveyed.

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“…As expected, the shift of the keto group to the adjacent position respective to isosteviol, does not affect the rigid skeleton of the molecule. The carbonyl group of the exocyclic substituent in position 4 eclipses the C3-C4 bond of the skeleton, which is the most favourable orientation since there are no hydrogen bonds, as for example in case of the methyl ester of isosteviol 15 or more bulky ester derivatives. 16 Isosteviol derivatives are known for the recognition of aromatic compounds and this behaviour is expressed in the molecular packing of compound 9 ( Figure 3), with 2-methoxyphenoxy substituents being located between the lipophilic polycyclic skeletons of the molecule.…”

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confidence: 99%

Synthesis and Reactivity of (+)-16-Deoxo-15-oxoisosteviol

Bomkamp¹,

Gottfried²,

Kataeva³

et al. 2008

Synthesis

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The synthesis of optically pure (-)-isosteviol derivatives with a keto function shifted to position 15 and its insertive esterification are described.Stevioside and rebauside F, which are both glycosides of the same aglycon, can be easily isolated from stevia plants and are used as alternative sweeteners. 1 Upon treatment with strong mineral acids, these readily available commercial mixtures provide (-)-isosteviol (1) in large quantities. 2 1 represents a unique diterpenoid skeleton with a keto and carbonyl group pointing in almost the same direction (Figure 1), and its co-crystallization with various organic compounds was studied intensively. 3 Recently, we exploited the high optical purity and the specific arrangement of functional groups for the construction of enantiomerically pure receptor structures based on triphenylene ketals. 4 In order to facilitate selective and optimal binding of guests, a more centred and therefore less open arrangement of the hydrogen bonding donors is crucial. 5 Since the host/guest interaction is almost insulated from the outer sphere, no self-aggregation phenomena are observed. 6 In order to close up the geometry of the (-)-isosteviol-based receptor, a shifting of the keto group from position 16 into the adjacent location 15 was envisioned. Standard protocols known from simple terpenoids, e.g. camphor, 7 were tested on the 16-oxobeyerane skeleton.In this paper we report the efficient translocation of the keto function onto position 15. Furthermore, a novel insertive esterification is described. The synthetic pathway required blocking of the carboxy moiety, which was performed by methylation of the carboxylate providing 2 in good yield. 8

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Unexpected bromination reaction of isosteviol methyl ester with bromoalkanes

Cited by 15 publications

References 1 publication

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

(–)‐Isosteviol as a Versatile Ex‐Chiral‐Pool Building Block for Organic Chemistry

Synthesis and Reactivity of (+)-16-Deoxo-15-oxoisosteviol

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