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New Synthetic approach to 1-hydroxy-p-menthane and its alkoxy ethers

Sangamesha, M.A. (2010) New Synthetic approach to 1-hydroxy-p-menthane and its alkoxy ethers. [Student Project Report]

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This Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page.

Item Type: Student Project Report
Additional Information: In the present study, a route to p-menthan-1-ol and its methyl and ethel ethers has been synthesised, these compounds could be prepared in high yields from p-menth-1-ene. The strategy applied here for the synthesis is new and offers clean reaction conditions. The stereochemistry of chiral vicinal-1,2-bromo alcohol at hydroxyl (methoxy and ethoxy) has been retained as the reagents only de-brominate the substrate. The reagent system InCl3-NaBH4 was earlier used for de-bromination of various bromo-substrate under radical type de-bromination.14 This successful method has been adopted for the first time into preparation of chiral monoterpenic oxygenated compounds. The title compound 1-hydroxy-p-menth-8-ene was earlier synthesized by using 2-bromo-1-hydroxy-p-menthane via epoxide route. The formation of epoxide by a base leads to trans-stereochemistry. This trans-epoxide is then converted to trans-β-terpineol by reducing using lithium aluminium hydride. The yield of the product is low as there is formation of neo-dihydrocarveol as side product. However, in the present investigation epoxide preparation step is reduced. Also, much stronger reducing and expensive reagent LAH as been avoided. This indirectly help in avoiding air sensitive reagent and also messy work-up conditions. Apart from this, presently applied reagents (InCl3 and Sodium borohydride) are easy to handle. Work-up procedures have been very clean and easily adoptable. The yields seems to be good as there is no side reactions expected. Also, the above strategy is applied to 2-bromo-1-methoxy-p-menthane and 2-bromo-1-ethoxy-p-menthane substrates wherein the hydroxyl group is replaced with methoxy- and ethoxy- groups. Here also similar results are obtained and the products 1-methoxy-p-menthane and 1-ethoxy-p-menthane are easily synthesized. In this case, product was qualitatively identified by GCMS studies. The present methodology is very useful in terpene chemistry as the chiral hydroxyl (methoxy- and ethoxy-) products may be used as chiral starting materials for natural product synthesis. The method may also be adopted to various similar kind of substrate to achieve required stereochemistry and required functionality at α–carbon atom adjacent to bromo-group. However, the reactivity of various iodo, chloro- and other group reactivity has not been studied and is open for development.
Uncontrolled Keywords: Monoterpenes; Essential Oils; terpenic hydrocarbons;
Subjects: 500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 24 Organic Chemistry
Divisions: Plantation Products Spices and Flavour Technology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 13 Aug 2010 11:11
Last Modified: 03 Jul 2015 07:38
URI: http://ir.cftri.com/id/eprint/9629

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