4272-10-0Relevant academic research and scientific papers
A single chiroptical spectroscopic method may not be able to establish the absolute configurations of diastereomers: Dimethylesters of hibiscus and garcinia acids
Polavarapu, Prasad L.,Donahue, Emily A.,Shanmugam, Ganesh,Scalmani, Giovanni,Hawkins, Edward K.,Rizzo, Carmelo,Ibnusaud, Ibrahim,Thomas, Grace,Habel, Deenamma,Sebastian, Dellamol
, p. 5665 - 5673 (2011)
Electronic circular dichroism (ECD), optical rotatory dispersion (ORD), and vibrational circular dichroism (VCD) spectra of hibiscus acid dimethyl ester have been measured and analyzed in combination with quantum chemical calculations of corresponding spectra. These results, along with those reported previously for garcinia acid dimethyl ester, reveal that none of these three (ECD, ORD, or VCD) spectroscopic methods, in isolation, can unequivocally establish the absolute configurations of diastereomers. This deficiency is eliminated when a combined spectral analysis of either ECD and VCD or ORD and VCD methods is used. It is also found that the ambiguities in the assignment of absolute configurations of diastereomers may also be overcome when unpolarized vibrational absorption is included in the spectral analysis.
Chiral γ-butyrolactones related to optically active 2-hydroxycitric acids
Ibnusaud, Ibrahim,Thomas, Puthiaparambil Tom,Rani, Rajasekharan Nair,Sasi, Paleapadam Vavan,Beena, Thomas,Hisham, Abdulkhader
, p. 4887 - 4892 (2002)
The complete spectroscopic data and other physical constants of two naturally occuring, diastereomeric, optically active γ-lactones derived from inexpensive 2-hydroxycitric acids, namely garcinia acid [(2S,3S)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid] and hibiscus acid [(2S,3R)-tetrahydro-3-hydroxy-5-oxo-2,3-furandicarboxylic acid] and related derivatives have been described for the first time.
Natural Product-Derived Chiral Pyrrolidine-2,5-diones, Their Molecular Structures and Conversion to Pharmacologically Important Skeletons
Habel, Deenamma,Nair, Divya S.,Kallingathodi, Zabeera,Mohan, Chithra,Pillai, Sarath M.,Nair, Rani R.,Thomas, Grace,Haleema, Simimole,Gopinath, Chithra,Abdul, Rinshad V.,Fritz, Matthew,Puente, Andrew R.,Johnson, Jordan L.,Polavarapu, Prasad L.,Ibnusaud, Ibrahim
, p. 2178 - 2190 (2020/07/08)
The versatility of the natural products (2S,3S)- and (2S,3R)-3-hydroxy-5-oxotetrahydrofuran-2,3-dicarboxylic acids (1 and 2), isolated in large amounts from tropical plant sources, has been demonstrated by the construction of 3-substituted and 3,4-disubstituted chiral pyrrolidine-2,5-diones. The absolute configurations of chiral pyrrolidine-2,5-diones have been ascertained using chiroptical spectroscopic methods and/or single-crystal XRD data. A combination of different reaction strategies delivering a diverse matrix of fused heterocyclic ring systems is presented. The pyrrolo[2,1-a]isoquinoline alkaloid (+)-crispine A possesses a wide range of pharmacological activities including antidepressant, antiplatelet, antileukemic, and anticancer activities. The analogues of indolizino[8,7-b]indole alkaloids (+)- and (-)-harmicine show strong antileishmanial, antinociceptive, PDE5-inhibitory, antimalarial, and antiviral activities. The bicyclic furo[2,3-b]pyrrolo skeleton is present in many natural products. Thus, the uniqueness of relatively cheap, naturally occurring chiral 2-hydroxycitric acid lactones as chirons has been demonstrated by the construction of some important molecular skeletons that are otherwise difficult to synthesize.
Stabilization of NaBH4 in Methanol Using a Catalytic Amount of NaOMe. Reduction of Esters and Lactones at Room Temperature without Solvent-Induced Loss of Hydride
Prasanth,Joseph, Ebbin,Abhijith,Nair,Ibnusaud, Ibrahim,Raskatov, Jevgenij,Singaram, Bakthan
, p. 1431 - 1440 (2018/02/09)
Rapid reaction of NaBH4 with MeOH precludes its use as a solvent for large-scale ester reductions. We have now learned that a catalytic amount of NaOMe (5 mol %) stabilizes NaBH4 solutions in methanol at 25 °C and permits the use of these solutions for the reduction of esters to alcohols. The generality of this reduction method was demonstrated using 22 esters including esters of naturally occurring chiral γ-butyrolactone containing dicarboxylic acids. This method permits the chemoselective reductions of esters in the presence of cyano and nitro groups and the reductive cyclization of a pyrrolidinedione ester to a fused five-membered furo[2,3-b]pyrrole and a (-)-crispine A analogue in high optical and chemical yields. Lactones, aliphatic esters, aromatic esters containing electron-withdrawing groups, and heteroaryl esters are reduced more rapidly than aryl esters containing electron-donating groups. The 11B NMR spectrum of the NaOMe-stabilized NaBH4 solutions showed a minor quartet due to monomethoxyborohydride (NaBH3OMe) that persisted up to 18 h at 25 °C. We postulate that NaBH3OMe is probably the active reducing agent. In support of this hypothesis, the activation barrier for hydride transfer from BH3(OMe)- onto benzoic acid methyl ester was calculated as 18.3 kcal/mol.
