Reverse prenyl group

Indolines 6 and 7 with reversed prenyl group were obtained by prenylboration of indole (90°C, 2 hs) and triptamine 5 (125°C, 8 hs) respectively. 

From an okara medium fermented with P. simplicissimum AHU 8402, three insecticidal compounds were isolated. Two of them were identified as 1 and 2, and the third one seemed to be a new, related compound, which was thus named okaramine C (4). Okaramine C (4), C32H36N4O3, proved to be a tetrahydro-derivative of 1. The -NMR and 1H-H COSY spectra indicated that 4 had an additional reverse-prenyl group, an exchangeable proton and a -CH2-CH< group instead of -CH=CH- and -CH=C<, suggesting that the C-r=C-2 double bond was saturated and... 

Okaramine J (11) had a molecular formula of C32H36N4O3, which is identical to the molecular formula of okaramine C (4). The H-NMR spectrum of 11 is shown in Fig. (4). The critical differences were the absence of one of two reverse-prenyl groups that were observed in 4 and the appearance of a new prenyl group and one exchangeable proton coupled to the methine proton at C-8a. The HMBC spectrum of 11 indicated that the prenyl group was bound to C-7 in the pyrroloindole ring [21]. 

Okaramine K (12), C32H34N4O3, had a molecular formula identical to that of okaramine G (8) [21]. The essential difference between the H-NMR spectra of 8 and 12 was the absence of a reverse-prenyl group... 

Intramolecular cyclization of 4 forms a tetrahydroazocine ring, leading to okaramine N (15). Oxidation at C-l of 15 gives okaramine O (16), which yields okaramine A (1) through dehydration between C-l and C-2 . On the other hand, aza-Claisen rearrangement of a reverse-prenyl group in 4, 16, and 1 leads to okaramines J (11), P (17), and H (9), respectively (Fig. (5) part 2). 

D (5) successively. Okaramine D (5) could be formed from the intermediate via 6 (Fig. 5 part 3). Removal of a reverse-prenyl group from 1 leads to okaramine I (10). 

Each of the tryptophan metabolites shown in Fig. (10) has prenyl groups, reverse-prenyl groups, and a diketopiperazine ring. Echinulin (57), which contains a tryptophan moiety, was isolated by Birch and Farrar in 1963 [40]. Neoechinulin (58), which contains a... 

Ser, Thr, and Tyr are often modified, either by heterocychzation to oxazole/oxazolme or by prenylation with DMAPP. The ease of spontaneous ring opening of oxazohne residues" " could explain the prevalence of unmodified Ser/Thr residues. Alternatively, enzyme specificity could explain this variability. The prenyl group is often in the reverse prenyl position, in which DMAPP has added at the 3-carbon instead of the 1 -carbon. 

Fig. 3. Reversible membrane association of lipidated proteins (redrawn firom Ref. [11]). (a) Binding of a ligand (shaded circle) to an iV-myristoylated protein triggers a myristoyl switch, (b) Binding of a ligand (shaded oval) to the polybasic motif of a singly lipidated protein reduces the second signal allowing the protein to desorb from membranes, (c) Phosphorylation within the polybasic motif lowers its affinity for anionic phospholipids (electrostatic switch), (d) A prenyl group is sequestered by a binding partner, (e) Lipidated secreted proteins (the star represents a lipid modification cholesterol and/or fatty acid) spread ftom their source by binding to lipoprotein carriers.

Okaramine P (17), C32H34N4O4, had the same molecular formula as 16. The H-NMR spectrum of 17 is characterized by the disappearance of the reverse-prenyl signals in 16 and the appearance of a prenyl group. The HMBC spectrum indicated that the prenyl group was connected to C-l. The relative stereochemistry of 17 was the same as that of 16 at all chiral... 

This unexpected result was interpreted to mean that the reverse prenyl transferase presents the olefinic n-system of DMAPP in a manner in which both faces of the n-system are susceptible to attack by the 2-position of the indole moiety. The simplest explanation is to invoke binding of the DMAPP in an upside down orientation relative to normal prenyl transferases which permits a facially non-selective S attack on the rr-system as shown in Scheme 20. It was speculated that in this situation the pyrophosphate group is likely anchored in the enzyme active site with the hydrophobic isopropenyl moiety being presented in a conformationally flexible (A B) disposition with respect to the tryptophan-derived substrate (Scheme 20). This is in contrast to the normal mode of prenyl transfer where the nucleophilic displacement at the pyrophosphate-bearing methylene carbon occurs with inversion of stereochemistry at carbon with the hydrophobic tail of DMAPP buried in the enzyme active site. 

Collective name for polyprenylated 2,3-dimethylben-zoquinone derivatives, [e.g., PQ-9 (n=9), C5jH ,02, Mr 749.22, bright yellow platelets, mp. 48-49 C, u max 314 nm (petroleum ether)], isolated from chloro-plasts. The P. play a role as redox substrates in photosynthesis for cyclic and non-cyclic electron transport where they are converted reversibly into the corresponding hydroquinones (plastoquinols). The biosynthesis of P. proceeds from homogentisic acid, a product of L-tyrosine degradation, through prenylation and methylation (methyl group from L-methionine) to the plastoquinols which are dehydrated to the P.. ... 

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