Diels-Alder type adducts

C, Further Reactions of the Diels-Alder Type Adducts... 

Acetylenedicarboxylic acid is known to combine with a number of pyrroles but only in the case of 1-benzylpyrrole have the products been rigorously examined. Mandell and Blanchard showed that in this case a mixture of the maleic anhydride (35), the fumaric acid (36), and the Diels-Alder type adduct (38) was formed. 

Treatment of l-ethylideneamino-3-methylindole 95 with p-toluene sulfonic acid in boiling benzene gave l,2-dihydro[l,2,4]triazino[l,6-a]indole 96 (75CPB2891). The reaction was said to be due to an initial formation of a Diels-Alder-type adduct followed by the liberation of 3-methylindole. Compound % was oxidized either on exposure to air or by the action of chloranil to give 97 (Scheme 24). 

Nomura T., Hano Y., Ueda S. Studies on the Optically Active Diels-Alder Type Adducts From Mulherry Tree Int. Congr. Ser. 1998 1157 379 390 Keywords mulberry tree, optically active Diels-Alder type adducts from mulberry tree... 

Keywords biosynthesis of mulberry Diels-Alder-type adducts, moraceae... 

The germabenzene species 15 reacts in two different fashions with a variety of substrates to give cylcoaddition products (Scheme 7).30 With MesCNO and 2,3-dimethylbutadiene, 15 behaves similarly to a compound with a single Ge-C double bond, whereas in reactions with styrene and phenylacetylene, 15 behaves as a 1-germabuta-l,3-diene to give Diels-Alder-type adducts. The germanium-carbon doubly bonded species 23 reacts with nitriles in several different ways, including as a 1,2-dipolar species with Bu CN, as a 1,4-dipolar species with PhCN, and as a base with various /3-functionalized nitriles (Scheme 8). 

The enamide 166 react with the cation radical of cyclohexadiene, which is generated by sensitized electron transfer with the photoexcited dicyanobenzene (DCB), to generate a Diels-Alder type adduct (equation 110)167. 

As a result of its reduced aromaticity, relative to pyrrole, furan undergoes [4 + 2] cycloaddition reactions much more readily. It combines as a diene with electron-poor dienophiles to yield Diels-Alder-type adducts. Maleic [(Z)-butenedioic acid] anhydride, for example, reacts at room temperature, and the only isolated adduct is the exo isomer (the more thermodynamically favoured adduct) (Scheme 6.27a). 

Shirota, O. et al., Antiandrogenic natural Diels-Alder-type adducts from Brosimum rubescens, J. Nat. Prod, 60, 997, 1997. 

Shinomiya, K. et al., A Diels-Alder-type adduct from Artocarpus heterophyllus. Phytochemistry, 40, 1317, 1995. 

Shi, Y.-Q., Fukai, T., and Nomura, T., Structure of sanggenon O, a Diels-Alder type adduct derived from a chalcone and a dehydroprenylated sanggenon-type flavanone from Morus cathayana, Heterocycles, 54, 639, 2001. 

Shen, R.-C. and Lin, M., Diels-Alder type adducts from Morus cathayana. Phytochemistry, 57, 1231, 2001. 

Hano, Y. et al., A novel way of determining the structure of artonin I, an optically active Diels-Alder type adduct, with the aid of an enzyme system of Morus alba cell cultures, J. Chem. Soc. Chem. Commun., 1177, 1992. 

Ferrari, F. et al., Multicaulisin, a new Diels-Alder type adduct from Morus multicaulis, Fitoterapia, 71, 213, 2000. 

The oxidation of 1-hydroxy-2,3,4,5-tetraphenylpyrrole in benzene by lead(lV) dioxide (68BSF4679) gave the radical 3 which was reduced back to the hydroxypyrrole by lithium aluminum hydride. Photosensitized oxidation gave the peroxynitrone 4, which was reduced by potassium iodide in acetic acid to 5 (68BSF4679). ALPhenylmaleimide reacts at room temperature with 1-hydroxypyrrole to give the Diels-Alder-type adduct 6,... 

As previously mentioned, short-life cycloalkynes add to reactive dienes such as l,3-diphenylbenzo[c]furan (16) and tetracyclone to give Diels-Alder-type adducts, and the reaction has frequently been used to establish the intermediacy of short-life cyclic acetylenes. The addition reactions have found synthetic applications - > > . The addition of 1-diethylaminobutadienc to cycloalkynes provides an interesting synthetic route for benzo annelation . Intervention of dehydrobullvalene was also confirmed by the formation of DicIs-Alder-type adducts - . At present only azides are used as 1,3 dipoles in the addition reaction with short-life cycloalkynes - - . ... 

The oxidation of dienes with molecular oxygen to form Diels-Alder-type adducts can be effected by Lewis acids and some salts of stable carbenium ions [33]. For ergos-teryl acetate, SbF is by far the most active catalyst (Eq. 17) [33a],... 

Keck also investigated asymmetric catalysis with a BINOL-derived titanium complex [102,103] for the Mukaiyama aldol reaction. The reaction of a-benzyloxyalde-hyde with Danishefsky s dienes as functionalized silyl enol ethers gave aldol products instead of hetero Diels-Alder cycloadducts (Sch. 40) [103], The aldol product can be transformed into hetero Diels-Alder type adducts by acid-catalyzed cyclization. The catalyst was prepared from BINOL and Ti(OPr )4, in 1 1 or 2 1 stoichiometry, and oven-dried MS 4A, in ether under reflux. They reported the catalyst to be of BINOL-Ti(OPr% structure. 

Chemistry and Biosynthesis of Natural Diels-Alder Type Adducts from Moraceous Plants... 

Mulberry tree is a rich source of intermolecular Diels-Alder type adducts coiq>rising two molecules of isoprenylphenols [26]. This article describes the chemistry of the Diels-Alder type adducts from moraceous plants and the biosynthesis of the adducts in Morus alba cell cultures. 

Other optically active Diels-Alder type adducts from moraceous plants... 

The compounds structurally similar to the mulberry Diels-Alder type adduct have also been isolated from the other species of the plants of the family Moraceae. Brosimones A (26) [41], B (27) [14] and D (28) [14] have been isolated from Brosimopsis oblongifolia, a Brazilian moraceous plant (Figure 7). They are expected to be formed through the same way as the mulberry Diels-Alder type adducts. Of these compounds, compound (26) is a unique adduct which may be formed through an intramolecular [4+2] cycloaddition reaction of the isoprenyl portion and the a, -double bond of the chalcone slceleton of compound (28) (Figure 8). Artonins C (29) [42], D (30) [42] and I (31) [43] isolated from Artocarpus heterophyllus, an Indonesian moraceous plant, can also be regarded... 

As described above, the stereochemistries of the mulberry Diels-Alder type adducts could be divided into the following two groups one is an all-trans in relative configuration and the other is a cis-trans configuration. All-trans type adduct may correspond to an exo-addition product in the Diels-Alder reaction of a chalcone and a dehydroprenylphenol, whereas a cis-trans type adduct corresponds to an endo-addition product in the reaction. 

Absolute stereochemistries of the mulberry Diels-Alder type adducts were confirmed by the circular dichroism (CD) spectroscopic evidence and by X-ray analysis [26, 52, 53]. 

Optical rotations ([a]o) of typical mulberry Diels-Alder type adducts are summarized in Table 1. The all-trans type adducts exhibit negative optical rotation, while the cis-trans type adducts exhibit positive values. Considering the absolute stereocheml-... 

As described in section 2, some cell strains of Moras alba callus tissues induced from the seedlings or the leaves have a high productivity of the mulberry Diels-Alder type adducts. The yields of major adducts chalcomoracin (21) and kuwanon J (11) by the cell strains are about 100 - 1000 times more than those of the intact plant [32]. The biosynthesis of the mulberry Diels-Alder type adducts has been studied with the aid of the excellent cell strains. 

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