Trans derivatives

In the case below, isomerized to ii, producing a trans derivative, but acetonide iii fails to isomerize to the internal derivative because the less favorable cis product would be formed. ... 

Reaction of p-nitrophenyl 2-(p-tolylsulfinyl)acetate 161 with aryl aldimines in the presence of imidazole was found to give /j-lactams 162 and amides 163206. In the cyclization, only the two 3,4-trans derivatives were formed out of a possible four diastereomeric pairs and, interestingly, the ratio of two diastereomeric pairs went up to 6.7 1. This means not only that internal asymmetric induction207 affords the trans derivative, but that also a relatively high asymmetric induction took place during the reaction. 

Chlorine adds to form the Zrans-dichloride bromine adds, in carbon tetrachloride solution, to give a mixture of as- and trans-dibromides this addition can be directed wholly to the trans derivative by conducting the bromination in a mixed phase reaction in aqueous suspension. 

The Hofmann degradation product 252 used for a synthesis of corynoline (254) was again a useful starting material for ( )-corydalic acid methyl ester (8). It was reduced with sodium cyanoborohydride to the trans derivative 10 as a major product, which was converted to 8 via acetal 268 and aldehyde 269 (143). 

On the basis of fundamental experiments (see Section IV,A,2) some indenobenzazepine alkaloids have been efficiently synthesized from the corresponding protoberberines via 8,14-cycloberbines. For example, the cycloberbine 428 derived from the protoberberine 427 was heated with methanesulfonic acid in aqueous tetrahydrofuran to afford a 2 1 mixture of cis- and trans-indenobenzazepines 429 in 92% yield (Scheme 85). The mixture was methylated with methyl iodide to give the cts-N-methyl derivative 430 and the unchanged trans secondary amine (21%), which was very difficult to methylate and which gave the /V-methyl derivative only in 6% yield even on treatment with dimethyl sulfate for 43 hr. Contrary to the ordinary cases (Section IV,A,2), the trans derivative did not isomerize to the cis isomer 430 under various acidic conditions. Debenzylation of 430 by hydrogenolysis afforded fumarofine (417), which was converted to O-methylfumarofine (316) by methylation with diazomethane (215). 

A more complex carbonylation process is involved in the formation of bisbutenolides (bifurandiones) from cobalt carbonyl-catalyzed carbonylation of alkynes112 117 (Scheme 68). The trans derivative (53) is formed in good yield from acetylene,112 but yields from substituted acetylenes (e.g., propyne)... 

In acidic aqueous solution the complexation of the chloroaqua derivatives of cis- and trans-DDP involves substitution of the aqua ligand with the nucleobase [15]. The trans derivative reacts 10 times faster than the cis isomer with inosine at pH 3, in line with the trans-effect Cl" > NH3. It has been shown that trans- [PtCl(NH3)2(H20)]+ behaves like a mono-... 

In studies of ion-molecule reactions in the gas phase, the influence of collision energy on competitive. S"n2 and. S"Ni reactions has been examined for reactions of epimeric indan-l,2-diols with the NH3-NH4+ system. Stereospeciflc. S"n2 and. S Ni pathways operate for the cis and trans derivatives, respectively. 

In all cases, mixtures of cis and trans diastereoisomers are reported. In terms of experimental observation, it is now possible to prepare 1,3-disubstituted tetrahydro-j8-carbolines and 1-substituted tetrahydro-/3-carbolines of known absolute stereochemistry. For example, if optically active A -benzyltryptophan methyl ester of known chirality reacts with aldehydes in refluxing benzene, the trans derivative is obtained. Arylglycidate was also used in the synthesis instead of aldehydes (78CPB2305). 

Much more work has been done on the cyclization of amides, mainly of enamides. There are examples of the use of N- chloroacetylbenzylamines to produce dihydroisoquinolin-4-ones (220) (74TL1181). Irradiation of enamides (221) can give either tetrahydrophenan-thridinones (71JOC3975) or hexahydrophenanthridinones (74JCS(P1)1747). Without added iodine a mixture of cis and trans derivatives is obtained and the ratio varies with solvent in non-polar solvents the trans cis ratio can be 15.6 1. If iodine is added to the solution to be irradiated, the quinol-2-ones are obtained. The mechanism has been discussed and... 

A conformational assignment to benzoylaziridines from IR spectra concluded (74SA(A)1471)that the c/sderivative(63, R = Ar) should have an s-cis conformation in order to be able to minimize steric interactions, while the s-trans conformation better applies to the trans derivative 64 in order to... 

The reactivity of a halogen compound in dehydrohalogenation over solid catalysts also depends on its steric arrangement. This was shown by studying the dehydrohalogenation of the rigid molecules l-bromo-1,2-diphenylethylene [188] and l-chloro-l,2-diphenylethylene [171] on catalysts of the type of metal salts and metal oxides the cis-compound was always more reactive than the trans-derivative. 

Oxidation of unsaturated fatty acids The oxidation of unsatu rated fatty acids provides less energy than that of saturated fatly I acids because they are less highly reduced and, therefore, tom I reducing equivalents can be produced from these structured Oxidation of monounsaturated fatty acids, such as 18 1(9) (deb acid) requires one additional enzyme, 3,2-enoyl CoA isomeras which converts the 3-cis derivative obtained after three rounds (3-oxidation to the 2-trans derivative that can serve as a substra for the hydratase. Oxidation of polyunsaturated fatty acids, sue ... 

The chain of the trans derivative 66t is formed by H-bonded cyclic pairs of carboxyl groups, and possesses but translational symmetry in the a direction"6 (Figure 16). This chain is thus chiral. Both chiral forms are found in the crystal, related by centers of... 

The 5-nitrofuryl group225 is promulgated as an efficacious moiety to ensure chemotherapeutic value, and the trans derivative (135) was found to be active against Staphylococcus aureus,171 It is also a broad-spectrum antimicrobial agent226 and an antischistosomal drug.227 The latter activity is due to reduction of the phosphorylase phosphatase in the worms themselves, damaging reproduction in the female.227, 228... 

In the case of both the Ns protected five- and six-membered heteocycles, the cis-conflgurated precursors were obtained more efficiently than the trans-configurated precursor. However, the introduction of the Cbz protecting group in the trans-derivatives resulted in quantitative conversion to the desired products. 

Anselmi et al. (02JCS(P2)1525), very recently published the conformational analysis and dynamics of cA/ rafts-4-methylcyclohexyl tetrahydro-pyranyl ethers (cf. Scheme 12) and compared their structures with the floral odors of the compounds. The cis isomer 40(cis), endowed with a main white flower note, has an bent, oval molecular shape. The trans derivatives 40(trans) and 41, exhibit different odors, possess an extended structure of cylindrical molecular shape. Brenna et al. (02CJC714) reexamined the configuration/conformation of rose oxide analogues. However, the conformational analysis provided poorer results than published previously (78JPC303) without even citing the previous paper. 

The m-dioxolane (94) on heating to 160 °C gives a trans-oxirane as shown in equation (13). The reaction proceeds in high yield for (94) while the corresponding trans derivative is stable under the same conditions. Both the cis and the trans compounds are converted stereospecifically into the cis and trans alkenes, respectively, on treatment with hot acetic anhydride (70TL5223). The reaction for the trans compound is shown in equation (14), and the mechanism for the transformation is discussed in Section 4.30.2.2.5. 

Early studies from the Pfizer laboratories had revealed that compounds from a series of mzn.s-l-amino-4-phenyl-tetralins possessed potent norepinephrine (NE) uptake blocking activity. The activity was highly specific for the (1/ , 4S)-enantiomer and was confined to the trans derivatives. The corresponding (IS, 4/ )-enantiomer was much less active and the diastereomeric cis racemates were inactive at blocking NE uptake. It was subsequently shown that many compounds from the diastereomeric cis senes were unexpectedly potent and selective inhibitors of serotonin (5-HT) uptake, thus differentiating these compounds from the trans compounds. One of these compounds, sertraline (5), was originally discovered as a racemic mixture. Resolution showed that the (+)-enantiomer was several times more selective for 5-HT uptake blocking activity than the (-)-isomer. The (+)-enantiomer was subsequently shown to possess the in vivo behavioral effects expected of a potent and selective 5-HT blocker. Thus, as opposed to... 

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