Nosylation

K2CO3 or CS2CO3, DMF or CH3CN, PhSH, 88-96% yield. This process is not always selective for p-nosylate cleavage. Some amines, especially cyclic ones, tend to form 4-phenyl thioethers by nitro displacement as by-products of the cleavage process. This seems to be true only for the p-nosylate. ... 

Electrolysis, DMF. In the case of primary nosylates, -NH deprotonation competes with cleavage. 

DBU, DMF, HSCH2CH2OH, >48% yield. These conditions were used to remove the nosyl group from A -methylated peptides." ... 

Jacobsen has utilized [(salen)Co]-catalyzed kinetic resolutions of tenninal epoxides to prepare N-nosyl aziridines with high levels of enantioselectivity [72], A range of racemic aryl and aliphatic epoxides are thus converted into aziridines in a four-step process, by sequential treatment with water (0.55 equivalents), Ns-NH-BOC, TFA, Ms20, and carbonate (Scheme 4.49). Despite the apparently lengthy procedure, overall yields of the product aziridines are excellent and only one chromatographic purification is required in the entire sequence. 

Scheme 8.23 Base-promoted macrocyclization of epoxy N-nosylate 88.

In a versatile stereocontrolled total synthesis of (+)-vinblastine, Fukuyama used a base-promoted macrocyclization of the N-nosylate and the terminal epoxide moiety present in 88 as one of the key steps, giving the 11-membered-ring product 89 in 82% yield (Scheme 8.23) [42],... 

Four members of the tetraponerine family (the major constituents of the contact poison of the New Guinean ant Tetraponera sp.) were prepared by RRM methods [156]. The key step leading to tetraponerine T7 (374) from the readily available cyclopentene precursor 372 is shown in Scheme 72. When compound 372 was exposed to catalyst A in the presence of ethylene, the desired ROM-RCM sequence proceeded smoothly to furnish heterocycle 373 with complete conversion, whereas the corresponding di-nosyl (2-nitrophenylsulfonyl)-protected analog of 372 led only to a 1 2 equilibrium mixture of starting material and RRM product. 

In 1952, Wolfrom and Hilton demonstrated that L-sorbose was also capable of forming dimeric dianhydrides,22 and they postulated sorbofuranosyl and pyra-nosyl cationic intermediates. In 1955, Boggs and Smith23 postulated a fructofu-ranosyl cationic intermediate in the formation of per-O-acetyl ot-D-Fru/-1,2 2,l -p-D-Fru/[di-D-fructose anhydride I (5)] from inulin triacetate. They indicated that three adjacent P-2,l -linked fructofuranosyl units would be required for formation of the dianhydride. 

From this observation of the inhibition by adenosine, and other observations, Newell and Tucker suspected the existence of a common synthetic pathway for adenosine and thiamine, and proved (with the help of a collection of mutants) that the bifurcation occurred after the 5-amino- l-(P-D-ribofura-nosyl)imidazole 5 -phosphate (46) step (Scheme 23). Finally, they found that 5-amino-l-(0-D-ribofuranosyl)imidazole (47), labeled with l4C in the imidazole ring, was incorporated into pyramine without significant loss of molar radioactivity by a mutant that is able to use this nucleoside (presumably after phosphorylation).53,54... 

Although halides are common leaving groups in nucleophilic substitution for synthetic purposes, it is often more convenient to use alcohols. Since OH does not leave from ordinary alcohols, it must be converted to a group that does leave. One way is protonation, mentioned above. Another is conversion to a reactive ester, most commonly a sulfonic ester. The sulfonic ester groups tosylate, brosylate, nosylate, and mesylate are better leaving groups than... 

Murphy et al. showed that EPHP [25] and L2P(0)H [26] can also be used in radical C-C bond forming reactions (Scheme 8). Recently, Piettre et al. [27] used the sodium salt of hypophosphorous acid as H-donor and the subsequent phosphonyl radical as phosphonylating agent for the preparation of 3-fura-nosyl-6 -furanosylphosphinate (Scheme 9). 

MIM 252500) Pseudo-Hurler ML III glycoprotein N-acetylglu-cosamininylphosphotrans-ferase. (Acid hydrolases thus lack phosphoman-nosyl residues.) As for ML II but deficiency Glycoprotein fragments... 

J. Lorquin, G. Lortet, M. Ferro, N. Mear, B. Dreyfus, J.-C. Prome, and C. Boivin, Nod factors from Sinorhizobium saheli and 5. teranga bv. sesbaniae are both arabi-nosylated and fucosylated, a structural feature specific to Sesbania rostrata symbionts. Molec. Plant Microbe Interact. I0 il9 (1997). 

The two overwhelming oxidation products of the purine moiety of dGuo 37 arising from the transformation of guanine radical cations 38 were isolated and identified as 2,2-diamino-4-[(2-deoxy-/l-D-eryfhro-pentofura-nosyl)amino]-5(2H)-oxazolone (41) and its precursor 2-amino-5-[(2-deoxy-... 

Gold-based catalysis has attracted considerable attention in recent years. A gold-catalyzed aziridination reaction has recently been reported <06JOC5876>. A series of gold catalysts were examined for their ability to catalyze the aziridination of styrene with p-nitrophenylsulfonamide (NsNH2). Styrene and phenyl-substituted styrenes provided the N-nosyl aziridines in good to excellent yields. Cinnamate however provided the aziridine product in only 25% yield. The use of other sulfonamides (e.g. tosyl, trichloroethyl) gave much lower yields of the aziridine product. 

Non-metal catalyzed aziridinations have also been reported. These methods are often more broadly applicable than the metal-catalyzed methods. The use of iV-methylpyrrolidine-2-one hydrotribromide (MPHT) and chloramine-T is an effective route for the synthesis of iV-tosyl aziridines <06MI16>. The aziridination of olefins using i-BuOI and sulfonamides appears to be a general method for aziridination <06CC3337>. The i-BuOI is prepared in situ from t-BuOCl and Nal. This is a broadly applicable method in that a wide variety of sulfonamides (tosyl, nosyl, SES) can be used with roughly equivalent yields. 

Typically, the stereospecific formation of quaternary centers is as problematic as selective nucleophilic attack at the more substituted carbon of aziridines. Interestingly, a copper mediated methodology has been reported that does both <060L5105>. Although N-tosyl aziridines show favorable results, A-nosyl aziridines gave the best results. The reaction of 89 with a variety of phenols yielded 90 in moderate yields. 

Catalytic hydrogenation of methanolic solutions of the 4-nitroimidazoles (72 R1 = D-glucopyranosyl, D-arabinopyranosyl, D-xylopyranosyl R2 = H) using platinum oxide as catalyst gave the corresponding 4-aminoimidazole nucleosides (71 R1 = D-glucopyranosyl, D-arabinopyra-nosyl, D-xylopyranosyl R2 = H) (yields 16, 33, and 25%, respectively), which were apparently isolated as the free bases but no mention of the stability of these compounds was made (72LA67). 

Similarly, treatment of the salt with 2,3,4,6-tetra-O-acetyl-a-D-glucopyra-nosyl bromide 46 gave 4-[2,3,4,6-tetra-0-acetyl-/3-D-glucopyranosyl]-4//-pyrido[2,3-e][l,2,4]triazin-3-one 1-oxide 47. Antileukemia tests for the 4-alkyl derivatives showed no activity. 

A similar scaffold for the preparation of peptidomimetics was prepared by Mitsunobu cyclization of the molecule coming from the coupling of 4-benzylprolinol and iV-nosyl(o-nitrobenzensulfonyl) tryptophan 316 (Scheme 41). A Mitsunobu cyclization occurred easily due to the acidity of the NH of the nosyl group that could be further selectively deprotected under very mild conditions. The so-formed bicyclic amine 317 can be further coupled with different amino acids to give compounds 318, employed in the search of a new somatostatin pharmacophore <2005BML4033>. 

Representative Procedure for Nosyl Chloride Promoted Glycosylation with Cl-Hemiacetal Donors 130... 

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