Five pentacyclic triterpenoids have been isolated from the minor constituents of local liquorice roots, one of them has not been isolated before from liquorice root. Their structural formulae and stereochemical configuration was determined by spectroscopic methods. 13C and 1H NMR data have been compiled.

The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. GTP is hydrolytically opened, converted into 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate leads to...

in this paper we define the removable cycle that, if $im$ is a class of graphs, $gin im$, the cycle $c$ in $g$ is called removable if $g-e(c)in im$. the removable cycles in eulerian graphs have been studied. we characterize eulerian graphs which contain two edge-disjoint removable cycles, and the necessary and sufficient conditions for eulerian graph to have removable cycles h...

[structure: see text] Two novel alkaloids with an unprecedented fused-pentacyclic skeleton, daphmanidins C (1) and D (2), have been isolated from the leaves of Daphniphyllum teijsmanii, and the structures were elucidated on the basis of spectroscopic data. The relative stereochemistry of 1 and 2 was assigned by combination of NOESY correlations and a simulation analysis. Daphmanidin C (1) eleva...

Kopsihainanine A (1), an unprecedented skeleton with a 6/5/6/6/6 pentacyclic rearranged ring system, together with a new biogenetically related compound, kopsihainanine B (2), were isolated from Kopsia hainanensis. Their structures were elucidated by means of spectroscopic methods. The absolute configuration of 1 was determined by ECD calculation.

[structure: see text] A novel C(27)N(3)-type pentacyclic Lycopodium alkaloid, lycoperine A (1) consisting of two octahydroquinoline rings and a piperidine ring, was isolated from the club moss Lycopodium hamiltonii. The structure and relative stereochemistry were elucidated on the basis of 2D NMR data and chemical transformation. Lycoperine A (1) exhibited an inhibitory activity against acetylc...

Synthetic efforts toward the chlorinated aza-propellane alkaloid acutumine (1) are described. The key vicinal quaternary centers were constructed by a photochemical [2 + 2] cycloaddition reaction of a furanyl-tetrahydroindolone. Dihydroxylation of the [2 + 2] product enabled a tandem retro-aldol/intramolecular ketalization reaction, which revealed the aza-propellane core of 1 while generating a...

The synthesis of a new type of pentacyclic benzothiazolium compound 6,13-dihydropyrazino[2,1-b:5,4-b ́]bis(1,3-benzothiazole)-7,14-diiumdibromide (2), is reported. Compound 2 was prepared by dimerization of 2-(bromomethyl)benzothiazole. Quantum chemical calculation studies have been carried out on the structures of possible isomers of 2, as well as the products of its deprotonation reactions.

Eight highly modified Daphniphyllum alkaloids with unprecedented fused hexa- or pentacyclic skeletons, daphnicyclidins A-H (1-8), have been isolated from the stems of Daphniphyllum humile and D.teijsmanni, and their structures were elucidated on the basis of spectroscopic data and chemical means. The stereochemistry was elucidated by combination of NOESY correlations, X-ray crystallographic dat...

[structure: see text]. The tetracyclic ketal 24, a suitable intermediate for the synthesis of antitumor pentacyclic quassinoids, has been efficiently prepared from communic acids (5a-c), via methyl ketone 9. The synthetic sequence from 9 to 24 consists of 15 steps in 12% overall yield.