Quassine

The Dlels-Alder reaction is a favourite way of introducing many chiral centres at once, and we saw examples of this in Chapter 36. Compound (31) was used in a synthesis of quassin." It has seven adjacent chiral centres. How many can bo introduced in one step by a Diels-Alder reaction and what should the starting materials be ... 

Isolation of two quassinoids (quassin and simalikalactone D) from root bark of Quassia africana Baill... 

T riterp. azadirachtin-like tetranortritero. azadirachtin (neem teee,Azadirachta indicaA. Juss., Meliaceae, Ang. MI) Quassinoids (biosynthetically related to triterp.) including seco- and further degraded forms Quassia amara L., Sapindales, Ang. from Jamaica quassin DSII, and other metabolites Connolly 1997). 

Picrasma quassioides (D. Don) Benn. P quassioides (D. Don) Benn. f. dasycarpa Kitag. Ku Shu (stem bark) 2.4- dichloro-6-aminopyridine, 4.5- dimethoxycanthin-6-one, 2.6- dimethoxy-p-benzo-quinone, methyl nigakinone, picrasmin, nigakihemiacetal A, nigakilactone A, nigakinone, quassin.50 Treat fever, stomachache. 

N.A. Quassinoids, ailanthone, quassin, alkaloids, flavonols, tannins." Antimalarial, against cancerous cells, counter worms, excessive vaginal discharge, gonorrhea, malaria, antispasmodic, cardiac depressant. 

N.A. Picrasma exeelsa (Sw.) Planch. Quassinoid (quassin), alkaloids, coumarin (scopoletin), vitamin B,.09 Strengthen digestive systems, increase bile flow, secretion of salivary juices, and stomach acid production. 

From the point of interest of antifeedants, triterpenoids can be divided into three classes, depending on the number of carbon atoms in the skeleton there are full C-30 triterpenes, C-26 limonoids, and C-20 quassins. In addition, there are saponins, which can have either a triterpenoid or a steroid skeleton. Interesting and powerful antifeedants are found in each class. 

Quassin is a bitter-tasting substance that can be extracted from the quassia tree (bitter tree, Picrasma quassioides Benn).156 It is said to be the most bitter substance found in nature. Quassin is used in traditional Chinese medicine. Besides quassin, modified triterpenes, the so-called quassinoid, are the principal component of the bitter taste. 

A Lewis-acid-catalysed Diels-Alder reaction of the diene (70) and the quinone (71) is the key step in the synthesis of compound (72) with the appropriate stereochemistry and functionality for conversion into quassin.53 The androstane derivative (73) has been transformed into (74) in model experiments towards the synthesis of quassin.54... 

Quassin (= Nigakilactone Ailanthus altissima, Picrasma spp., Bitter... 

Note. Two other classes of methylated spirits are recognised in the United Kingdom mineralised methylated spirits and denatured ethanol. Mineralised methylated spirits is ethanol of an appropriate strength, 90 parts by volume mixed with wood naphtha 9.5 parts by volume and crude pyridine 0.5 parts by volume, and to every 2000 litres of this mixture is added 7.5 litres of mineral naphtha (petroleum oil) and 3.0 g of methyl violet. Denatured ethanol is ethanol, of a strength not less than 85% v/v, 98 parts by volume mixed with propanol 2 parts by volume, and to the resulting mixture is added denatonium benzoate 10 pg/ml, or solid quassin 120 pg/ml, or sucrose octa-acetate 4000 pg/ml. 

A synthesis of ( )-quassin relies on the AlCh-catalyzed Diels-Alder reaction (292) + (293) (294),... 

Figure 5 Biological activities associated with quassinoids, from Simaroubaceae species, may not be linked to a common mechanism of action/ Different testing procedures have indicated insecticidal activity for quassin, anticancer activity for quassimarin (also present in Quassia amara) and antimalarial activity for simalikalactone-D/...

Denatonium benzoate is among the most bitter of substances known and is detectable at concentrations of approximately 10 ppb. In pharmaceutical and other industrial applications it is added to some products as a deterrent to accidental ingestion. It is most commonly used at levels of 5-500 ppm. Denatonium benzoate may also be used to replace brucine or quassin as a denaturant for ethanol. 

The 2-methoxy-4a-methyl-5Q -androst-2-en-l-one system (500), corresponding to the ring a substitution pattern of quassin, has been elaborated from a 5a-androst-l-en-3-one by application of a sequence of familiar transformations.5,6(8-Epoxy-4/3-hydroxy-5/3-cholest-2-en-l-one (501) has been synthesized as a model for rings A and B of withaferin A (502). The synthesis involved multiple steps from cholesta-2,5-dien-l-one related compounds were synthesized from the 2,4-dien-l-one." ... 

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