ライフサイエンスコーパス: oxocarbenium

1 beta-anomers 1 and 2 and their corresponding oxocarbenium 3, coupled with relaxed potential energy su

2 or the direct attack of acetyl-lysine on an oxocarbenium ADP-ribose intermediate is proposed.

3 shown to catalyze both Mukaiyama-Mannich and oxocarbenium aldol reactions with high efficiency and en

4 tal formation coupled with a selective axial oxocarbenium allylation allowed for the preparation of t

5 carbonyl compounds are resonance hybrids of oxocarbenium and carboxonium ions, while the latter are

6 ed through the monomer alpha-addition to the oxocarbenium and was controlled by the reversible deacti

7 c investigations support the formation of an oxocarbenium by way of an atom transfer radical addition

8 stereoselective reduction of the appropriate oxocarbenium cation and a highly chemo- and diastereosel

9 ic bond yields an intermediate comprising an oxocarbenium cation and a uracilate anion.

10 y, the electrophilic ribose 1' carbon of the oxocarbenium cation is subject of an attack by the nitro

11 mics that are capable of allylic rather than oxocarbenium cation stabilization.

12 tive axial reduction of an in situ generated oxocarbenium cation to assemble the beta-C-glycoside moi

13 logs of 3-AB with capacity to react with the oxocarbenium cation.

14 s, PtxS1 activates NAD+ to form the reactive oxocarbenium cation.

15 ves a configurationally stable zwitterionic (oxocarbenium cation/vinyl carbanion) intermediate, which

16 tereoselective reductions of the appropriate oxocarbenium cations that were derived from a common del

17 process involving three transient (a)cyclic oxocarbenium cations, the breaking of three single C(sp(

18 bond of inosine by nucleoside hydrolase has oxocarbenium character and a protonated leaving group hy

19 er in a loose transition state which retains oxocarbenium character in the ribose.

20 etween the alkyl copper intermediate and the oxocarbenium electrophile takes place with inversion of

21 id zinc triflate to promote the formation of oxocarbenium electrophiles through the activation of die

22 elative leaving group activation and ribosyl-oxocarbenium-forming abilities of these enzymes.

23 id catalysis hinged upon the formation of an oxocarbenium intermediate accompanied by subsequent alco

24 g catalysis, activating carbonyls to form an oxocarbenium intermediate and enabling hydride transfer

25 n followed by oxidation to form a 5-membered oxocarbenium intermediate and subsequent nucleophilic ri

26 proposed by M. D. Erion et al., in which an oxocarbenium intermediate is stabilized by phosphate and

27 Since the vinylic oxocarbenium intermediate is trapped by chlorite ion to

28 alpha-halo carbonyls and aryl amines via an oxocarbenium intermediate.

29 ments), with the concomitant formation of an oxocarbenium intermediate.

30 elimination with concomitant formation of an oxocarbenium intermediate.

31 tion mechanisms and to estimate lifetimes of oxocarbenium intermediates and their dependence on the g

32 s a novel safeguarding mechanism by trapping oxocarbenium intermediates and, hence, minimizing stereo

33 According to the BBAH, nucleophiles add to oxocarbenium intermediates by S(N)2-like antiperiplanar

34 amide combination promotes the generation of oxocarbenium intermediates from acetal substrates at low

35 tent with a mechanism involving formation of oxocarbenium intermediates or transition states during t

36 sumably via the in situ formation of alkenyl-oxocarbenium intermediates, which eliminates the need fo

37 eophile addition, thus ruling out long-lived oxocarbenium intermediates.

38 its breakdown by charge stabilization of the oxocarbenium intermediates/transition states.

39 on between the cationic carbon center of the oxocarbenium ion and the heteroatom substituent.

40 n this scenario, both faces of the prochiral oxocarbenium ion are subject to nucleophilic addition to

41 each case, reinforcing the involvement of an oxocarbenium ion as the common intermediate of this cruc

42 hion through the intermediacy of a transient oxocarbenium ion at C2 of PEP.

43 t ion complex between the PCCP anion and the oxocarbenium ion chain end prevents chain-transfer event

44 e, the deoxyribose ring exhibits significant oxocarbenium ion character with bond breaking (r(C-N) =

45 bond via a transition state with substantial oxocarbenium ion character, resulting in short-lived oxo

46 The ribose ring has strong oxocarbenium ion character.

47 stabilize transition states with pronounced oxocarbenium ion character.

48 sociative transition state has a significant oxocarbenium ion character.

49 ions parallels the relative stability of the oxocarbenium ion conformers involved, as assessed by cal

50 nic acid induces transient chain breaks with oxocarbenium ion formation and subsequent intramolecular

51 e H-bond interaction with the enzyme and (2) oxocarbenium ion formation in the ribosyl ring.

52 ohol transposition, carbonyl group trapping, oxocarbenium ion formation, and nucleophilic addition re

53 distorted to a conformation favoring ribosyl oxocarbenium ion formation.

54 n aldehyde or ketone, thus leading to cyclic oxocarbenium ion formation.

55 Herein, we leverage CAD-induced oxocarbenium ion generation to trigger ultraviolet photo

56 In this reaction, TMSOTf is used to form the oxocarbenium ion in situ under conditions compatible wit

57 to occur within the active site to bring the oxocarbenium ion intermediate and Glu 89 closer by 4-5 A

58 This reaction proceeded through an oxocarbenium ion intermediate and the asymmetric inducti

59 n, and hydride donors, able to react with an oxocarbenium ion intermediate derived from furanosidic s

60 e experimental findings, suggesting that the oxocarbenium ion intermediate is responsible for the deg

61 oceed via a nonstabilized, aliphatic, cyclic oxocarbenium ion intermediate paired with the confined c

62 ld provide electrostatic stabilization of an oxocarbenium ion intermediate that is formed by dissocia

63 1 by a hydrogen exposes an enzyme-stabilized oxocarbenium ion intermediate to reaction with external

64 ChEWL, which is postulated to stabilize the oxocarbenium ion intermediate, has no counterpart in GoE

65 2-oxonia-Cope rearrangements by way of a (Z)-oxocarbenium ion intermediate.

66 t rupture of the C1'-N1 bond resulting in an oxocarbenium ion intermediate.

67 ese results can be understood by considering oxocarbenium ion intermediates and their conformational

68 t C(2) and the two tau bonds (bent bonds) of oxocarbenium ion intermediates formed under the glycosyl

69 splace one of the two bent bonds of bicyclic oxocarbenium ion intermediates in an antiperiplanar fash

70 ibuted to rates of nucleophilic additions to oxocarbenium ion intermediates that approach the diffusi

71 ating groups on the nucleophilic addition to oxocarbenium ion intermediates.

72 demonstrating that products are formed from oxocarbenium ion intermediates.

73 y the chiral catalyst to generate a reactive oxocarbenium ion is invoked.

74 uranosyl cis-dioxolenium ion versus the open oxocarbenium ion is much higher than the pyranosyl syste

75 er, the region of IR that corresponds to the oxocarbenium ion is translocated in the direction of the

76 ven less reactive substrates, and the formed oxocarbenium ion makes the carbonyl more electrophilic f

77 ), namely, a metal-binding site and glycosyl oxocarbenium ion mimic.

78 ransition state stabilization of the ribosyl oxocarbenium ion occur from neighboring group interactio

79 be disfavored by destabilizing the resultant oxocarbenium ion or by stabilizing an intermediate tetra

80 ilic substitution reactions that proceed via oxocarbenium ion or carbocation intermediates.

81 toms (O5 and C2 atoms), similar to either an oxocarbenium ion or N-acetylgalactal form, which are cry

82 nonmetallo KDO8PS, in which water attacks an oxocarbenium ion or PEP from the si side of C2.

83 ently linked anomeric phosphates rather than oxocarbenium ion pairs as the reactive intermediates.

84 Currently, the oxocarbenium ion pathway is indicated to be solely respo

85 nucleobases most likely via the traditional oxocarbenium ion pathway.

86 lying that RpfB acts via the formation of an oxocarbenium ion rather than a covalent intermediate.

87 rmodynamically favorable C-3 position of the oxocarbenium ion rather than the anomeric center.

88 c systems, invoking an intermediate glycosyl oxocarbenium ion reacting through a boat conformation.

89 e stereochemistry of monomer addition to the oxocarbenium ion reactive chain end.

90 ypical Prins cyclization conditions when the oxocarbenium ion resulting from the rearrangement is sim

91 ocation and of formaldehyde to give a simple oxocarbenium ion results in very little change in the re

92 n to more readily approach and stabilize the oxocarbenium ion that forms and the deprotonation transi

93 the 3-position of enol ethers, generating an oxocarbenium ion that is trapped by a carboxylic acid nu

94 ite of HOBt followed by the extrusion of the oxocarbenium ion that was attacked by the glycosyl accep

95 tes by a cationic gold(I) catalyst yields an oxocarbenium ion that we previously showed is trapped by

96 reoselective capture of an in situ generated oxocarbenium ion via an intramolecular Friedel-Crafts al

97 lysis intermediates (an oxazoline ion and an oxocarbenium ion) to a family 19 barley chitinase.

98 esence of an axial alkoxy group distorts the oxocarbenium ion, changing its inherent preferences for

99 n largely considered as the chemistry of the oxocarbenium ion, e.g., direct rupture of the C1'-N1 bon

100 stent with additions to a halogen-stabilized oxocarbenium ion, not a three-membered-ring halonium ion

101 r) of the dipyrrin framework with an allylic oxocarbenium ion, provides easy access to BODIPY-carbohy

102 proach is anti to the C-2 substituent of the oxocarbenium ion, regardless of the ground-state conform

103 lization proceeding directly through a vinyl oxocarbenium ion, simulations identified an alternative

104 A highly stereoselective oxocarbenium ion-alkene cyclization for synthesis of C-b

105 The protocol has as a key step a novel oxocarbenium ion-enol ether cyclization to give a C1-sub

106 nium ion character, resulting in short-lived oxocarbenium ion-like species.

107 a direct displacement mechanism involving an oxocarbenium ion-like transition state assisted with Asp

108 aximizing stabilization of the corresponding oxocarbenium ion-like transition state during hydrolysis

109 ctivation mechanism with the formation of an oxocarbenium ion-like transition state, a hypothesis tha

110 (NAD(+)) has been proposed to go through an oxocarbenium ion-like transition state.

111 e which, due to its being unable to form the oxocarbenium ion-like transition states used by fucosylt

112 so highlights a tandem Lewis acid-catalyzed, oxocarbenium ion-mediated diastereoselective syn-allylat

113 ilar to or lower in energy than the starting oxocarbenium ion.

114 e lower energy ground-state conformer of the oxocarbenium ion.

115 honate or phosphinate group to the transient oxocarbenium ion.

116 be expected for maximal stabilization of an oxocarbenium ion.

117 ereoelectronic requirements for an incipient oxocarbenium ion.

118 favored over allylation of the intermediate oxocarbenium ion.

119 triggered by the selective generation of an oxocarbenium ion.

120 group with the exocyclic triple bond and the oxocarbenium ion.

121 a conformationally mobile transient glycosyl oxocarbenium ion.

122 guishing the faces of the diaryl-substituted oxocarbenium ion.

123 rded and predicted lifetimes for the cognate oxocarbenium ion.

124 the interaction between the catalyst and the oxocarbenium ion.

125 ic bimolecular nucleophilic addition into an oxocarbenium ion.

126 el stereoselectivities for attack on a given oxocarbenium ion.

127 ic anti aldol reaction and a two-directional oxocarbenium ion/vinyl silane condensation were employed

128 We have developed an oxocarbenium-ion-initiated cascade annulation that provi

129 t the enzyme stabilizes a highly dissociated oxocarbenium ionlike transition state with very low bond

130 es (X-C-OSiR(3), singlet and triplet state), oxocarbenium ions (X-CH-OSiR(3)(+)), and their hydrogen

131 port a reaction manifold involving both open oxocarbenium ions and cis-dioxolenium ions to provide th

132 which leads to generation of characteristic oxocarbenium ions and impairs glycosite localization.

133 effects governing the stability of furanosyl oxocarbenium ions and thiacarbenium ions are very simila

134 lyl cyanide with five- and six-membered ring oxocarbenium ions are attributed to the high reactivity

135 ehydes while reductions of the five-membered oxocarbenium ions are consistent with Woerpel's models.

136 Oxocarbenium ions are important reactive intermediates w

137 Acyclic ketone-derived oxocarbenium ions are involved as intermediates in numer

138 Asymmetric, catalytic reactions of oxocarbenium ions are reported.

139 investigations confirmed that the open-form oxocarbenium ions are the reactive intermediates involve

140 pical carbon-based nucleophiles (sp(2) C) on oxocarbenium ions are very different, with the former be

141 ucleophilic substitution reactions of cyclic oxocarbenium ions at high reaction rates are discussed.

142 y in reductions of alpha-silyloxy 5-membered oxocarbenium ions based on stereoelectronic effects are

143 reduced stabilization afforded to furanosyl oxocarbenium ions by covalent triflate formation.

144 The additions of nucleophiles to oxocarbenium ions derived from oxasilacyclopentane aceta

145 "inside attack" model for five-membered ring oxocarbenium ions developed previously for tetrahydrofur

146 lowest energy conformers of the intermediate oxocarbenium ions display the C-3 alkoxy group in a pseu

147 e Prins cyclization of the sulfur-stabilized oxocarbenium ions generated from acetals 14a-e or 15a-e

148 stituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions have been computed using the second-or

149 Among them, primary oxocarbenium ions have been much less explored, in part

150 henylsilyl (TBDPS) silyl protected rhamnosyl oxocarbenium ions have no facial selectivity except for

151 Nucleophilic attack on seven-membered-ring oxocarbenium ions is generally highly stereoselective.

152 for 2,3-trans-substituted five-membered ring oxocarbenium ions is strongly influenced by the presence

153 eactions and the similarity of the thia- and oxocarbenium ions make thio- ribo-furanosides excellent

154 at nucleophilic attack on five-membered ring oxocarbenium ions occurs from the inside face of the env

155 Different oxocarbenium ions such as those derived from dihydroisob

156 lic attack of putative intermediate glycosyl oxocarbenium ions suggests that the observed selectiviti

157 Vinyl ethers can be protonated to generate oxocarbenium ions that react with Me3SiCN to form cyanoh

158 ative cleavage reactions can be used to form oxocarbenium ions that react with pendent epoxides to fo

159 xo-trig cyclization led to the generation of oxocarbenium ions that were trapped to provide the glyco

160 nzoquinone (DDQ) to form persistent aromatic oxocarbenium ions through oxidative carbon-hydrogen clea

161 work in concert to enable the generation of oxocarbenium ions under mild conditions.

162 f in situ-generated cationic aryl 2-oxadiene oxocarbenium ions with alkenes.

163 stituted alpha-methoxystyrenes (X-1) to form oxocarbenium ions X-2(+) in 50/50 (v/v) HOH/DOD were cal

164 reactions of the acetals, which proceed via oxocarbenium ions, are operating under Felkin-Anh contro

165 proceeded via pseudoequatorially substituted oxocarbenium ions, as would be expected by consideration

166 kyl groups favor equatorial positions in the oxocarbenium ions, but alkoxy groups prefer axial confor

167 oordinated carbocations, such as iminium and oxocarbenium ions, have been applied in catalytic enanti

168 nformational preferences of the intermediate oxocarbenium ions, including the mannosyl cation, as wel

169 ed via cationic species: allylic cations and oxocarbenium ions, respectively.

170 ons of acyclic ketone-derived trisubstituted oxocarbenium ions, thereby providing access to highly en

171 ing stereoselective attack on naked glycosyl oxocarbenium ions.

172 d through either stabilized or nonstabilized oxocarbenium ions.

173 owever, proceeded via pseudoaxially oriented oxocarbenium ions.

174 e face as the substituent in C-2-substituted oxocarbenium ions.

175 to the stabilization of halogen-substituted oxocarbenium ions.

176 hat of reactions involving six-membered-ring oxocarbenium ions.

177 sfully used in enantioselective additions to oxocarbenium ions.

178 s to enantioselective additions to prochiral oxocarbenium ions.

179 density functional theory calculations, the oxocarbenium is generated through atom transfer and subs

180 The positive charge of the ribose oxocarbenium is stabilized by delocalization between the

181 molecules are electronically similar to the oxocarbenium-like dissociative hPNP transition state, DA

182 idic bonds by stabilizing positively charged oxocarbenium-like intermediates/transition states throug

183 ith water as an acceptor and the other is an oxocarbenium-like product, presumably through an S(N)1-l

184 ects are remarkable because they indicate an oxocarbenium-like ribose ring at the transition state bu

185 ates, or even increasingly unstable glycosyl oxocarbenium-like species, among which only alpha-glycos

186 of a positive charge at mannosyl C1, as the oxocarbenium-like transition state is approached, is com

187 bond hydrolysis due to stabilization of the oxocarbenium-like transition state.

188 A metal triflate catalyzed acyloxy oxocarbenium-mediated ring opening of the tandem reactio

189 copyranosyl-2,5-imino-D-mannitol (DDGIM), an oxocarbenium mimic, was solved to 2.5 A resolution.

190 diates containing vinylgold(I) and prochiral oxocarbenium moieties.

191 An oxocarbenium-olefin cross metathesis occurs during Brons

192 er and control experiments shed light on the oxocarbenium-olefin metathesis/rearrangement process as

193 anistic pathways: nucleophilic, radical, and oxocarbenium routes.

194 leavage and a nucleophilic addition onto the oxocarbenium species (in particular a Hosomi-Sakurai-typ

195 oxylation of the alkynol segment to give the oxocarbenium species (via cyclic enol-ether) followed by

196 hod is expanded by the generation of alkenyl-oxocarbenium species as highly activated alkene intermed

197 mics, as the protonated amine, the transient oxocarbenium species of the enzymatic reaction.

198 osylases have been proposed to go through an oxocarbenium species that would trap the 6-hydroxyl moie

199 ate, products and a mimetic of the transient oxocarbenium species, which were prepared by synthesis.

200 of which proceed through the same transient oxocarbenium species.

201 water molecule by the reactive intermediary oxocarbenium species.

202 owed by the addition of carboxylate onto the oxocarbenium that delivers the oxaspirolactone scaffold.

203 ectivity of the nucleophilic attack onto the oxocarbenium to afford the gamma-amino ester, gamma-imin

204 e reversible deactivation of the propagating oxocarbenium to form the glycosyl fluoride dormant speci

205 ferential attack on the opposite face of the oxocarbenium to the C2-H2 bond and that eclipsing intera

206 om the reaction mixture biased the transient oxocarbenium towards alpha-deprotonation that precedes a

207 GDP-2F-alpha-d-mannose, for which a cationic oxocarbenium transition state would be destabilized by e

208 ing that the D22 anion stabilizes a cationic oxocarbenium transition state.

209 ribose-C1" suggests that it may stabilize an oxocarbenium transition-state during the first step of t

210 ate is consistent with the involvement of an oxocarbenium transition-state structure, which has been

211 ions between the squaramide catalyst and the oxocarbenium triflate.

212 The other involves a transient oxocarbenium zwitterionic intermediate, formed by direct