Structure, chemistry and stereochemistry of rastevione, a sequiterpenoid from the genus stevia

Chemistry of renieramycins. Part 6: Transformation of renieramycin M into jorumycin and renieramycin J including oxidative degradation products, mimosamycin, renierone, and renierol acetate

“…1.2. 6,7,9,14,14a,12,9R,14aS (s, C-16), 61.5 (t, C-22), 61.0 (q, OCH 3 ), 60.9 (q, OCH 3 ), 58.7 (t, C-21), 58.7 (d, C-1), 57.2 (d, C-13), 54.8 (d, C-3), 52.2 (d, C-11), 41.1 (q, NCH 3 ), 26.2 (t, C-4), 22.7 (t, C-14), 8.7 (q, 7-cyano-6,7,9,14,14a,15-hexahydro-2,11-dimethoxy-3,12,16-tri-methyl-(6S,7S,9R, 14aS,15R)-(2)-6,15-imino-4H-isoquino[3,2-b][3]benzazocine-1, 4,10,13(9H)-tetrone (6). Acetyl chloride (9.4 ml, 0.13 mmol) was added to a solution of 3 (16.4 mg, 0.033 mmol), triethylamine (9.2 ml, 0.0066 mmol), and 4-dimethylaminopyridine (8.1 mg, 0.0066 mmol) in dichloromethane (4 ml) at 0 8C, and the reaction mixture was stirred at 25 8C for 1 h. The reaction mixture was diluted with water (20 ml) and extracted with dichloromethane (20 ml£3).…”

“…Catalytic hydrogenation of the unsaturated ester residue in 1m followed by alkaline hydrolysis also gave unsatisfactory results. 6 Furthermore, numerous attempts at the hydrolysis of the ester side chain of 1m under acidic conditions were unsuccessful. 7 By contrast, the reduction of 1m with lithium aluminium hydride in THF at 0 8C for 1 h gave the alcohol 3 (25.8%) along with restored the starting material 1m (15.0%).…”

Novel Sesquiterpenoid Skeletons by Wagner–Meerwein Rearrangements of Longipinane-9,13-diol-1-one Derivatives

“…In order to generate more reactive functionalities, compounds 2 , 3 , and 5 were prepared and subsequently rearranged with boron trifluoride etherate (Scheme ). The C-13 angelate group of 1 was selectively removed by a controlled alkaline hydrolysis using KOH in MeOH at room temperature to afford 2 , while the total alkaline hydrolysis of 1 using KOH in MeOH under reflux yielded 3 . Treatment of 2 with boron trifluoride etherate in CH 2 Cl 2 at 40 °C for 3 h afforded the two rearranged products, (3 R ,4 R ,5 R ,6 S ,9 R ,10 S ,11 S )-11,13-oxyneomorelian-1-one ( 10 ), obtained in 46% yield, and (4 S ,5 R ,6 S ,8 S ,10 R )-10,13-oxyneojiquilp-2-en-1-one ( 11 ), obtained in 29% yield.…”

“…The most representative constituents of the genus Stevia (Asteraceae) are longipinane derivatives, which can be classified into 18 types according to their degree of oxygenation and the position of the functional groups . They are usually functionalized at C-1, C-7, C-8, C-9, and/or C-13, with those functionalized at C-13 being less frequently found in Nature. − The inherent strain of the four-membered ring in the longipinane skeleton favors its expansion under acid or alkaline rearrangement conditions when a suitable adjacent leaving group is present. It is known that the degree of functionalization and stereochemistry of the functional groups present in the longipinane skeleton are decisive in directing the rearrangements toward the six- or the seven-membered ring.…”

Antifeedant and Cytotoxic Activity of Longipinane Derivatives

“…1), are generally found as complex mixtures of esters [6]. The relative stereochemistry of the C7, C8, and C9 acyloxy groups at the seven-membered ring was established by singlecrystal X-ray diffraction of rastevione acetate (10) [7] and by chemical transformation of rastevione (9) in compounds of type 1 and 3 [8]. The absolute configuration of this group of substances was found to be the same as (+)-longipinene and was established by comparing the electronic circular dichroism (ECD) curves of 1 and its diacetate 2 with vulgarone B [9].…”