Halogenated chamigrane sesquiterpenes from Laurencia okamurae
Xiao-Dong Li1, Wei Ding, Feng-Ping Miao
1Gansu Agricultural University, Lanzhou, 730070, China; Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, 264003, China.
Magnetic Resonance in Chemistry : MRC
|February 23, 2012
Summary
Marine red algae Laurencia okamurae yielded three new halogenated chamigrane sesquiterpenes, laurokamin A-C. Their structures were determined, and the antimicrobial activity of laurokamin A-C was evaluated.
Area of Science:
- Marine Natural Products Chemistry
- Organic Chemistry
- Phycology
Background:
- Marine red algae, particularly the Laurencia genus, are prolific sources of structurally diverse halogenated sesquiterpenes.
- These compounds often exhibit significant biological activities, including antimicrobial properties.
- Laurencia okamurae is a known producer of unique chamigrane sesquiterpenes.
Purpose of the Study:
- To isolate and characterize novel halogenated sesquiterpenes from Laurencia okamurae.
- To determine the chemical structures of the isolated compounds using advanced spectroscopic techniques.
- To evaluate the antimicrobial potential of the newly identified compounds.
Main Methods:
- Extraction and isolation of secondary metabolites from Laurencia okamurae.
- Structure elucidation using one-dimensional (1D) and two-dimensional (2D) Nuclear Magnetic Resonance (NMR) spectroscopy.
- Mass spectrometry (MS) for molecular weight determination and fragmentation analysis.
- Antimicrobial activity assays for compounds 1-3.
Main Results:
- Isolation of three new halogenated chamigrane sesquiterpenes: laurokamin A (1), laurokamin B (2), and laurokamin C (3).
- Identification of four known halogenated chamigrane sesquiterpenes: 10-bromo-α-chamigrene (4), 10-bromo-β-chamigrene (5), 2,10-dibromo-3-chloro-β-chamigrene (6), and obtusane (7).
- Unambiguous structural determination of all isolated compounds through comprehensive spectroscopic analysis.
Conclusions:
- The marine red alga Laurencia okamurae from Rongcheng, China, is a source of diverse halogenated chamigrane sesquiterpenes.
- Laurokamin A-C represent new additions to the known chemical diversity of Laurencia sesquiterpenes.
- Further investigation into the biological activities of these compounds is warranted, starting with their antimicrobial potential.
More Related Videos
Related Concept Videos
02:46Halogenation of Alkenes
Halogenation is the addition of chlorine or bromine across the double bond in an alkene to yield a vicinal dihalide. The reaction occurs in the presence of inert and non-nucleophilic solvents, such as methylene chloride, chloroform, or carbon tetrachloride.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
Consider the bromination of cyclopentene. Molecular bromine is polarized in the proximity of the π electrons of cyclopentene. An electrophilic bromine atom adds across the double bond, forming a cyclic bromonium ion intermediate.
01:33Radical Halogenation: Stereochemistry
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
Halogenation to form a new chiral center:
01:28Multiple Halogenation of Methyl Ketones: Haloform Reaction
A method involving the transformation of methyl ketones to carboxylic acids using excess base and halogen is called the haloform reaction. It begins with the deprotonation of α hydrogen to form an enolate ion which reacts with the electrophilic halogen to give an α-halo ketone. The step continues until all the α protons are substituted to form a trihalomethyl ketone. The resulting molecule is unstable, and in the presence of a hydroxide base, it readily undergoes nucleophilic acyl substitution.
02:45Alkyl Halides
Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
01:22Mass Spectrometry: Alkyl Halide Fragmentation
Chlorine isotopes exist as 35Cl and 37Cl in a 3:1 ratio, while bromine isotopes exist as 79Br and 81Br in a 1:1 ratio. The mass spectrum of alkyl halides typically produces two distinct molecular ion peaks, the molecular ion peak, [M], and the molecular ion plus two, [M + 2] peak. The relative heights of these two peaks are proportional to the isotopic abundance ratios of the halide. For example, 2‐chloropropane and 1‐bromopropane display two peaks with relative peak heights in a 3:1 and 1:1...
00:51Base-Promoted α-Halogenation of Aldehydes and Ketones
α-Halogenation of aldehydes and ketones is a reaction involving the substitution of α hydrogens with halogens in the presence of a base. The reaction begins with the abstraction of α hydrogen by the base to produce a nucleophilic enolate ion. This intermediate undergoes a subsequent nucleophilic substitution with the halogen to produce a monohalogenated carbonyl compound. If the starting substrate has more than one α hydrogen, it is difficult to stop the reaction at the stage of...