Minor bases

Apart from these methods of producing the opium alkaloids of commercial importance, processes for the minor bases have been published by Merck,Hesse, Plugge and Lohmann-Siedler. ... 

The hyoscine system occurs alone in certain northern Duboisia myo-poroides, and forms scopine, -tropine, dihydroxytropane and, in Datura meieloides, teloidine. Of these amino-alcohols, all the scopine is esterified by tropic acid and the minor bases by tiglic, methylbutyric or isovaleric acid, which contain the isoprene skeleton and are presumed to arise from that source. 

Fig. 5 Charge transfer occurs through the DNA /r-stack and is strongly dependent on minor base stack perturbations. Photoinduced electron transfer is observed from tethered intercalated ethidium to a rhodium intercalator bound to DNA up to 30 A away. The efficiency of electron transfer is drastically reduced in the presence of a stacking disruption, here a single base-pair mismatch... 

The ED, located in the southern El, is divided into West Gabbro, Discovery, and South Gold zones that are hosted by the BRM, the Elmtree Formation, and/or by the Chaleurs Group. The Discovery Zone (DZ) consists of several zones of polymetallic base-metal veins, whereas the South Gold Zone and WGZ consists of fine-grained disseminated sulfides and very minor base-metal veins. 

FIGURE 8-5 Some minor purine and pyrimidine bases shown as the nucleosides (a) Minor bases of DNA. 5-Methylcytidine occurs in the DNA of animals and higher plants, A/6-methyladenosine in bacterial DNA, and 5-hydroxymethylcytidine in the DNA of bacteria infected with certain bacteriophages (b) Sbme minor bases of tRNAs Inosine contains the basehypoxanthine. Note that pseudouridine, like uridine, contains uracil they are distinct in the point of attachment to the ribose—in uridine, uracil is attached through N-1, the usual attachment point for pyrimidines in pseudouridine, through C-5. 

The nomenclature for the minor bases can be confusing. Like the major bases, many have common names— hypoxanthine, for example, shown as its nucleoside inosine in Figure 8-5. When an atom in the purine or pyrimidine ring is substituted, the usual convention (used... 

A synthesis of arecoline (17) from acetaldehyde has been described.17 Sederine (18) is a minor base occurring in Sedum acre-, its structure has been settled by spectral and chemical study, but its stereochemistry has yet to be established.18 A new total synthesis of racemic solenopsin A (19) (fire-ant venom) has been published the pathway is outlined in Scheme 2.19... 

Search for the structures of methyl nucleosides in tRNA and suggest spectral characteristics that distinguish these minor bases from their corresponding parent (major) bases. 

At the early stages of the reaction, contribution of the autoxidation to the product distribution is thought to be minor based on the following observations, although some autoxidation pathway may be involved to a minor extent after slow accumulation of possible initiators. 

The structure of (—)-sedinine, an alkaloid of several Sedum spp., must be modified to (12), with the double-bond at C(3)-C(4) rather than at C(4)-C(5), as a consequence of X-ray diffraction analyses of the base and of its hydrochloride (12) also represents its absolute configuration.18 Sedacryptine is a new minor base from S. acre a single-crystal X-ray analysis of the free base points to structure and relative stereochemistry (13).19 The alkaloid could be identical with hydroxy-sedinone , isolated earlier.20... 

Alkaloids of Aconitum yesoense Nakai.—Sakai and co-workers42 have reported the isolation and elucidation of the structure of three new C19 diterpenoid alkaloids from Aconitum yesoense Nakai. These minor bases, ezochasmanine, ezo-chasmaconitine, and anisoezochasmaconitine, were isolated together with pseudo-kobusine (92), chasmanine (59), and jesaconitine (93). Ezochasmanine (94) (C25H41N07 m.pt 115—118 °C) formed a mixture of the monoacetate (95) and the diacetate (96) when treated with acetic anhydride in pyridine. The reaction of... 

A (-)-homaline synthesis, which is adaptable for the synthesis of the natural unsymmetrical Homalium alkaloids, is given in Scheme VI/11 [40] [41]. The eight-membered diaza part, VI/52, was synthesized by a transamidation reaction. It was possible to prepare homaline (VI/50) and the three other minor bases, hopromine, hopromalinol, and hoprominol, by combination of different eight-membered ring building blocks. As shown in Scheme VI/11, homaline (VI/50) was synthesized in 36% yield. 

In a recent study of this minor base, Olivier et al. (57) have deduced a close structural affinity with picraline, and have tentatively proposed the structure LXXXIX. 

The occurrence of reserpine has been reported from all Rauwolfia species, with the exception of about half a dozen in which it is probably present in minute amounts. Renoxidine, the A-oxide of reserpine, has been isolated from R. vomitoria, R. serpentina, and R. canescens, and it may not be a natural product, since it could have been derived by autoxi-dation of the tertiary base which is abundant in these plants. If it was an artifact, the occurrence of other analogous A-oxides should have been noted, but so far the only other recognized case is raujemidine A-oxide, which is found along with the parent alkaloid, raujemidine (a minor base of R. canescens). In contrast to reserpine, deserpidine and rescinnamine are of restricted distribution, each being recognized so far in about ten species only. 

The minor base hypoxanthine (X) occurs in some transfer RNA s. It is comparable to guanine but lacks the N(2) amino group. Therefore, all hydrogen bonds can be formed with cytosine and uracil where this group is not essential. For the hypoxanthine-cytosine interaction, we can write the matrix ... 

The mercury complexes of neutral uracil and dihydrouracil, the latter being a minor base found in tRNAs, reveal an unusual mode of coordination, wherein Hg + is bound not to the endocyclic N-3, which is blocked by a proton, but rather to the exocyclic atom O, which is a stronger donor atom than The usual binding to N-3 of deprotonated U... 

Hall (1964) used whole snake venom and bacterial alkaline phosphatase to prepare nucleosides from mixed sRNA in a search for minor bases (Hall 1965). 

Chemical modifications in the structure of nucleic acids often occur at the base level. The resulting modified bases and their detection is then of extreme importance to biochemists. Monitoring the action of chemothera-peutics is often accomplished by looking at base fragments. Similarly, the results of various illnesses can be assessed by the detection of given modified bases. Mass spectra of silylated cytosine and one of the minor bases in mammalian DNA, 5-methylcytosine, have been used as a tool for determining the ratio of these two bases from hydrolysates of nucleic acids.The intensities of the molecular ions of both disilylated bases (m/z 269/240) have also been used for the preparation of semiempirical curves that enable the detection of up to 1.6 pmol of 5-methylcytosine. However, the derivatization of modified bases has become less popular because of the possibility of removing this modification by a facile 8 2 reaction. ... 

Change in DNA minor base composition can be observed as a decreased level of methylation of the base 5-methyl deoxycytidine. 

Sederine which co-occurs with sedacryptine in S. acre has structure (24) (Hootele", J.P. Etienne and B. Colan, Bull.Soc. chim.Beiges, 1979, 88, 111).. Other minor bases of this plant are sedinone (25) and dihydrosedinine (26), but the most abundant alkaloid is sedacrine which has the constitution (27) (B. Colan and Hootele, Canad. J.Chem., 1983, 61, 470). 

Hetidine (C21H27NO4). An X-ray analysis of the hydriodide of this minor base from A. heterophyllum showed it to have structure (4), from which it follows that hetidine is (5) (absolute stereochemistry assumed). Its anomalous u.v. spectrum (A ,a,j 209 nm, e 5200) and its biosynthetic interest will be discussed later. 

Tylophorine, tylophorinidine, and O-methyl tylophorinidine have been isolated from roots of Pergularia pallida7 One minor base from this species has been identified as 3,6,7-trimethoxyphenanthroindolizidine, identical with the compound obtained by hydrogenolysis of O-methyl tylophorinidine. ... 

D, Roget D, Teoule R. Chemical synthesis of a biologically active natural tRNA with its minor bases. Nucleic Acids Res 20 5159-5166, 1992. 

Numerous reports have also been published on the separation of the individual alkaloids by using ion exchangers (301, 302), various solvents of different pH (303), or multibuffered extraction systems (102, 103, 304-306). The isolation of minor bases from extracts of P. somniferum (254,282, 307-311) and of Fumaria officinalis (166) has been reported. The separation of the bases obtained from this plant material was also carried out by countercurrent distribution (312) and column chromatography (313, 314). The alkaloid coreximine was detected in P. somniferum by an isotope dilution method which was based on the biosynthesis of this alkaloid from reticuline (249). The isoquinoline type of quaternary alkaloids can be... 

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