Clausines

Sec also Carnot, Nicolas Leonard Sadi Clausins, Rudolf Julius Emmanuel Culture and Energy Usage Ethical and Moral Aspects of Energy Use Gibbs, Jonah Willard Industiy and Business, History of Energy Use and Joule, James Prescott Kinetic Energy, Historical Evolution of the Use of Mayer, Julius Robert von Refining, History of Thomson, William Watt, James. 

In 1996, Wu et al. reported the isolation of clausine E (25) from the stem bark of C. excavata (46). One year later, Ito et al. reported the isolation of the same alkaloid from the same source and named it clauszoline-I (25) (47). This alkaloid showed inhibition of rabbit platelet aggregation and caused vasocontraction. The UV, IR, and H-NMR spectra were similar to those of mukoeic acid (10) with respect to the position of substituents. The presence of a carbomethoxy group at C-3 was indicated by an IR band at 1703 cm . Moreover, two significant mass fragments at m/z 210 (M —OMe) and 182 (M —COOMe) confirmed the presence of a carbomethoxy group. On the basis of these spectral data, structure 25 was assigned to clausine E (clauszoline-I) (Scheme 2.6). 

In 1992, Wu et al. isolated two new 4-prenylcarbazole alkaloids, clausine D (29) and clausine F (32), from the stem bark of C. excavata, collected in Taiwan. These alkaloids showed inhibition of platelet aggregation (50). Four years later, clausine 1 (30) was isolated from the same natural source, along with clausine E (25). This alkaloid showed inhibition of rabbit platelet aggregation and caused vasocontraction (46). Clausine 1 (30) and clausine E (25) have the same molecular formula. However, clausine 1 (30) is regioisomeric to lansine (69) (see Scheme 2.14). In the same year, clausine J (31a) and clausine G (33) were isolated from the same natural source (51) (Scheme 2.7). 

The UV spectrum (7max 225,242,253,276,289, and 351 nm) of clausine D (29) was similar to that of O-demethylmurrayanine (24), which also represents a 3-formyl-l-hydroxycarbazole framework. The presence of a hydroxy group and a conjugated aldehyde group was further supported by strong absorptions at 3380 and 1655 cm in the IR spectrum. The H-NMR spectrum was very similar to that of O-demethylmurrayanine, except for the presence of a prenyl group ( 1.65,... 

Clausine R (34) was isolated from the acetone extract of the root bark of C. excavata (43). The UV spectrum (2max 241, 282, and 320 nm) resembled that of mukoeic acid (10) (see Scheme 2.4), which indicated a 1-oxygenated 3-carboxycarba-zole framework. The H-NMR spectrum is similar to that of clausine Q (19) (see Scheme 2.5), except for the presence of a carbomethoxy signal at 5 3.86 instead of the aldehyde proton at 10.01 as in clausine Q. The presence of a carbomethoxy group... 

The UV, IR, and H-NMR spectra of clausine K (clauszoline-J) (51) were almost identical to those of clausine H (clauszoline-C) (50). The most significant difference between their spectra was the presence of IR bands at v ax 3315 (br) and 1666 cm and the absence of one methoxy group resonance in the H-NMR spectrum, which indicated the presence of a carboxy group instead of a carbomethoxy group at C-3 of the carbazole framework. This conclusion was supported by two characteristic mass fragments at m/z 254 (M —OH) and 226 (M" —COOH). The spectroscopic evidence combined with NOE experiments led to structure 51 for clausine K (clauszoline-J). This assignment was confirmed by methylation of 51 with diazomethane to afford clausine H (50) (46) (Scheme 2.11). 

Wu et al. isolated mukonidine (54) along with its O-methyl derivative, clausine L (39) (see Scheme 2.9) (59). However, the spectroscopic and physical data of Chakraborty s O-methylmukonidine were not identical with those of clausine L (59,78). Based on the agreement of the data of synthetic mukonidine with those of Wu s mukonidine (59), it was concluded that Chakraborty s mukonidine (78) may have a different structure (79-81). The UV, IR, and H-NMR spectra of mukonidine... 

In 1996, Ito et al. reported the isolation of clauszoline-D (82) and clauszoline-F (84) from the stem bark of C. excavata (74). Clauszoline-D (82) was obtained from nature in racemic form. Three years later, Wu et al. described the isolation of clausine U (83) and clausenatine A (85) from the acetone extract of the root bark of the same natural source (43). Clausine U (83) was isolated in optically active form ([a]o—72.85, c 0.0151, MeOH). However, the absolute stereochemistry of clausine U is still unknown (43). Prior to the isolation of clausenatine A (85), Furukawa et al. reported in 1993 the isolation of the same natural product from the root and stem bark of M. koenigii and named it mukoenine-B (82) (Scheme 2.16). 

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