ライフサイエンスコーパス: membered ring

1 hietane is feasible, leaving intact the four-membered ring.

2 macrolactone, or direct cyclization to a 12-membered ring.

3 an imino-to-sulfur substitution in the five-membered ring.

4 assembly, also synthesizes the embedded four-membered ring.

5 thereby blocking cyclization to a third six-membered ring.

6 cyano functionalities to annulate a new five-membered ring.

7 two naphthoquinone units connected by a five-membered ring.

8 Enyne metathesis is used to form the 14-membered ring.

9 fully substituted and highly oxygenated five-membered ring.

10 y of the conformational changes of the eight-membered ring.

11 owing for more functional variation on the 6-membered ring.

12 de), and Mitsunobu reaction to form the four-membered ring.

13 due to smaller hindrance for a five vs a six membered ring.

14 ctive exo-Diels-Alder reaction to form the 6-membered ring.

15 nar hexagonal B36 cluster with a central six-membered ring.

16 n mild activation sufficed to close the five membered ring.

17 Cgamma of the ligand giving a boat-like six-membered ring.

18 ient manner followed by cyclization of the 8-membered ring.

19 ing late-stage creation of the central seven-membered ring.

20 oms bridged by carbene groups yielding seven-membered rings.

21 teristics, such as windows that comprise odd-membered rings.

22 o [6 + 4] cycloaddition to form unbridged 10-membered rings.

23 orward fashion, including six- through eight-membered rings.

24 2] manner to give rise to seven- and/or five-membered rings.

25 ular Diels-Alder (TADA) reactions with 10-18-membered rings.

26 nal diolefins when affording smaller than 12-membered rings.

27 aliphatic cyclic ethers with four- to seven-membered rings.

28 etic transformations for the assembly of six-membered rings.

29 h aryl and vinyl halides, and five- to seven-membered rings.

30 significant delocalization around the three-membered rings.

31 double bonds, leading to benzannulated four-membered rings.

32 n to a strong pi-conjugation within the five-membered rings.

33 (8), given the inherent angle strain in five-membered rings.

34 irocyclic imines with five-, six-, and seven-membered rings.

35 ular cycloaddition reaction producing 5 to 7-membered rings.

36 ns within sofa-type conformation for the six-membered rings.

37 t are stitched together by lines of 8- and 4-membered rings.

38 three C4F8 moieties that form six- and seven-membered rings.

39 d by strong paratropic ring currents in four-membered rings.

40 titution on the strength of C-H bonds in six-membered rings.

41 ctional compounds and oxygen-containing five-membered rings.

42 cyclohexadiene rings trans-fused to 4- or 6-membered rings.

43 d five-membered rings, in preference to four membered rings.

44 m ions have been imaged sitting inside the 7-membered rings.

45 charged core composed of a series of fused 6-membered rings.

46 hat the final structure consists of only six-membered rings.

47 dialene-like structures at the proximal five-membered rings.

48 a transition states involving six- and seven-membered rings (1,5 and 1,6 H-shifts, respectively) of a

49 ved with the unbleachable analogue, 11-cis-6-membered ring (11-cis-6mr)-retinal, which has therapeuti

50 hemistry: (1) conformational analysis of six-membered rings, (2) evaluation of stereoelectronic inter

51 of the nitrile imine into 4pi-electron three-membered-ring 3-methyl-1H-diazirine, which photorearrang

52 (1)J(C-H) one-bond coupling constants in six-membered rings, (3) eclipsed conformation in cis-2-tert-

53 (2) structures incorporating seven- or eight-membered rings, (3) selective heteroatom doping, and (4)

54 m its intrinsic population of strained three-membered rings (3MRs) along with its chainlike aggregati

55 he expected cyclization product with a seven-membered ring, 4-methyl-2,3-dihydro-1H-pyrrolo[2,1-d][1,

56 Si:Al ratios, the volumetric density of six-membered-rings (6MR) containing two Al (2Al sites) is co

57 ction, known to occur predominantly in the 8-membered ring (8MR) pockets of MOR, is used as a site-sp

58 ane that consists of two triply entwined 114-membered rings, a molecular link.

59 arrangement of substituents on one of its 5-membered rings, a pattern shared by a number of other te

60 ysts are effective for the formation of five-membered rings, a ruthenium-based system that affords th

61 ]tetraphene, which "unexpectedly" forms five-membered rings accompanying highly selective 1,2-shift o

62 c acid (APCH), which is constrained by a six-membered ring across its Calpha-Cbeta bond.

63 spin trap, leading to the formation of a six-membered ring adduct, occurs through a very favorable pa

64 ck-Matsuda reaction of five-, six- and seven-membered ring alkenes and aryl diazonium salts is presen

65 the conformational flexibility of the seven-membered ring allows the carbonyl to be oriented perpend

66 charge is located in the central fused five-membered rings) allows the formation of a maximum of two

67 y enantioselective addition to racemic seven-membered-ring allyl chlorides for the first time.

68 strates for FPP synthase, giving novel seven-membered ring analogues of GPP and FPP.

69 nthesis of biaryl sultams containing a seven-membered ring and analogous sultones are also presented.

70 eophilic displacement reaction forming a six-membered ring and releasing a stable cationic reporter i

71 catalysed fragmentation to install the seven-membered ring and vicinal quaternary stereocentres of th

72 ting of 40 uranyl polyhedra linked into five-membered rings and 16 nitrate groups surrounds this cage

73 formal pentalene subunit at the central five-membered rings and [5]-radialene-like structures at the

74 ediated Yamamoto reaction to close the seven-membered rings and create the borepins 4a-c.

75 finally discussing the achievement of seven-membered rings and mixed heterocyclic motifs.

76 membered rings, with a particular focus on 5-membered rings and their modifications.

77 nt effects ring contraction to a strained 10-membered ring, and that strain in turn drives the Cope r

78 The reaction generates 5- to 9-membered rings, and of the 44 examples studied, 10 inclu

79 the approach by preparing recifeiolide (a 12-membered-ring antibiotic) and pacritinib (an 18-membered

80 The methods of synthesis of 5-membered rings are classified into two types: methods in

81 rings are cis-fused and the five- and three-membered rings are mutually trans, provides a synthetic

82 Carbo- and heterocycles of five- and six-membered rings are obtained in good yields.

83 acene derivatives with externally fused five-membered rings are prepared by means of a key palladium-

84 s the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely u

85 enes, which contain four linearly fused five-membered rings, are benchtop stable and behave as hole-t

86 th other electron-rich heteroaromatics and 6-membered ring aromatics provided they had donor groups i

87 Optimization studies identified a five-membered ring as the preferred conformational lock of th

88 s not limited to products that contain three-membered rings, as reductive opening by SmI2 can be used

89 The chair preference of a seven-membered ring at the fluorine transfer transition state

90 These seven-membered-ring aza ketones are prepared in good yield wit

91 Suitable substitution of the five-membered ring backbone exemplarily allowed the Co-cataly

92 s affords diverse functionality on the eight-membered ring backbone.

93 ion) and methods that start from preformed 5-membered rings, based mainly on cycloaddition reactions.

94 s showed that electron donation on the three-membered ring boosted the TOF of ring opening.

95 ed the ketone and dipolarophile to give five-membered rings but mixtures resulted with four atoms in

96 go subsequent functionalization in the seven-membered ring by a regioselective bromination-eliminatio

97 e conformational equilibria of the heterosix-membered ring by low temperature (13)C NMR spectroscopy

98 -bisallylaldehydes rearrange to generate six-membered rings by a mechanism triggered by aldehyde C-H

99 e seven-membered ring hydrogen bond and five-membered ring C(4-5-10-13-14) cyclization, from which th

100 tures a type-I beta-turn with a canonical 10-membered ring C=O-H-N hydrogen bond between backbone ami

101 solated from natural sources and include a 5-membered ring carbocycle.

102 to the methods of synthesis of 3-, 4- and 6-membered ring carbocyclic nucleosides, a selection of th

103 The five-membered ring carbodiimide is a stable structure, possib

104 e inorganic framework bearing the largest 18-membered-ring channels in gallium phosphites, denoted as

105 t the linking bond, stable nonracemizing six-membered ring chelates can be formed.

106 p was tethered to the acetal group by a five-membered ring compared to one where it was tethered by a

107 hey are mainly hexadecamers, with each eight-membered ring composed of one or two (in Archaea) or eig

108 studied, all efforts to synthesize the five-membered ring compound have thus far met with failure.

109 re close to 0 degrees , but in five- and six-membered ring compounds and in open-chain compounds the

110 rtion of the catalytic domain, such as a six-membered ring, confer selectivity for HKs.

111 a supported our hypothesis that the rigid 12-membered ring containing an alpha,beta-unsaturated carbo

112 chemical lead structure, consisting of an 11-membered ring, containing three nonconjugated C horizont

113 , containing two double bonds, or into a six-membered ring, containing two double bonds and a sixth a

114 p-pi orbital by incorporating it into a five-membered ring, containing two double bonds, or into a si

115 ic acid led to jadomycin AVA, a second eight-membered ring-containing jadomycin.

116 ategy may potentially enable access to all 7-membered-ring-containing Lycopodium alkaloids and provid

117 uctures, the paddlewheel moiety is a Pd four-membered ring coordinated by bridging carboxylic ligands

118 e-pot sequence for constructing the common 7-membered-ring core system, followed by either a biomimet

119 ween binuclear Cu(I) sites and N2O in the 10-membered rings Cu-ZSM-5.

120 is located in the intersection of the two 10 membered rings, Cu-MOR provides two distinct local struc

121 ion of a fused-ring benzazirine into a seven-membered ring cyclic ketenimine.

122 activation processes proceed through a five-membered-ring cyclometallated intermediate.

123 ters is described, proceeding through a four-membered-ring cyclopalladation pathway.

124 activation mode that proceeds through a four-membered-ring cyclopalladation pathway.

125 contains one of three different cyclic five-membered rings: cyclopentadiene, furan, or thiophene.

126 the first time that RE-MOFs with double six-membered ring (d6R) secondary building units are isolate

127 tive nets with a vertex figure as double six-membered-ring (d6R) building unit, namely the (4,12)-coo

128 nic center, lying at the junction of two six-membered rings, defines the conformation of the substrat

129 Distribution of produced five- or seven-membered rings depends on the substitution pattern on th

130 idine-2-caboxylic acid, a more flexible four-membered ring derivative of proline, shows relaxed eIF5A

131 ropionamide, reveals a common Li-N-Li-N four-membered-ring dimeric structure motif.

132 myo-inositol products via a 1,2-bridged five-membered ring dioxolanylium ion intermediate observed by

133 migration processes are observed in the five-membered ring due to the high barrier to 1,3-hydrogen mi

134 ained amide, amine, and hetero-aromatic five-membered rings, each of which had a hetero-atom and an u

135 niline)s with 9 and 13 collinearly fused six-membered rings employed Pd-catalyzed aminations and Frie

136 bered-ring antibiotic) and pacritinib (an 18-membered-ring enzyme inhibitor), the Z-isomer of which i

137 s preferentially bind the substrate as a six-membered ring, exposing the exact same sites to the atta

138 irements for uranium to bond to a small four-membered ring favours pi-bonding, utilizing 5f- instead

139 , five benzene rings fused to a central five-membered ring, for binding of six alkali-metal ions.

140 Galactofuranose (Galf) is the five-membered ring form of galactose.

141 hway proceeds via the initial step of a five-membered ring formation upon attack of the hydrazine, fo

142 s proposed to account for the selective five-membered-ring formation with the rearrangement of the ar

143 and the systems with fused benzene and a six-membered ring formed atropisomers separated by a barrier

144 ples accounting for the preparation of eight-membered rings from bis(allenes) in the absence of metal

145 ptor affords densely functionalized 5- and 6-membered rings from ynoate-enoate, ynoate-enenitrile, an

146 rentiating among these isomers in their five-membered ring furanose structure and smaller energetic d

147 tenolide to produce stereoselectively a five-membered ring fused bicyclic lactone, the core structure

148 ionenes (spiro-ionenes) containing 5- and 6-membered rings fused by central nitrogen cations.

149 Introduction of ring strain through five-membered ring fusion at the NC bond slightly increased t

150 mics studies of the seven-, eight-, and nine-membered rings gave additional structures, which were th

151 ty is strongly ring size dependent, with six-membered rings giving exclusively alpha-benzyl pentenoli

152 carried out to form seven-membered and eight-membered rings, giving rise to tetranitro dipyrazolo-1,3

153 rivatives (containing five-, six-, and seven-membered rings) have been investigated.

154 utive aza-Michael additions assemble the six-membered ring heterocycle, while in the second domino pr

155 yl groups as acceptor and benzannulated five-membered ring heterocycles with alkyl chains of varied l

156 ne have shown reliable selectivity with five-membered-ring heterocycles.

157 etatheses to afford the 5- as well as the 14-membered ring, however, with mixed success in terms of E

158 doubly locked configuration, i.e., the seven-membered ring hydrogen bond and five-membered ring C(4-5

159 es revealed that the syn isomer favors a six-membered ring hydrogen bond to nitrogen and the anti iso

160 o nitrogen and the anti isomer favors a five-membered ring hydrogen bond to oxygen.

161 f each Gln sidechain participates in a seven-membered ring hydrogen bond with the backbone NH of the

162 g intramolecular hydrogen bonds within a six-membered ring in the enones and the enols.

163 mediate to form an energetically stable four-membered ring in the singlet state.

164 of a large diversity of highly functional 7-membered rings in good yields up to 95%.

165 4-disubstituted carbo- and heterocyclic five-membered rings in high yields and with good to excellent

166 e moieties with differently substituted five-membered rings in the backbone of the newly formed heter

167 -substituted benzene units to construct five-membered rings in this work provides a unique entry to n

168 abolite, comprises a linear array of 10 five-membered rings in two pentacyclic regions that derive fr

169 tramolecular hydroacylation has favored five-membered rings, in preference to four membered rings.

170 A five-membered ring indene skeleton is also prepared via olefi

171 le or multiple hydrophilic moieties on a six-membered ring inhibited the Hh pathway in both Hh-depend

172 By low-temperature NMR spectroscopy the six-membered-ring interconversion could be frozen at 103 K a

173 sp(3) C-H bonds of methyl groups via a five-membered ring intermediate over the sp(2) C-H bonds of a

174 C-H bonds of beta-methyl groups, via a five-membered ring intermediate, over the aromatic sp(2) C-H

175 addition with the nitrone, generating a five-membered ring intermediate.

176 de-based coupling reagent DIC leads to a six-membered-ring intermediate acting as a versatile precurs

177 ssible cycloadditions, a pair of novel three-membered ring intermediates has been discovered.

178 N-N bond formation, producing unstable five-membered ring intermediates that spontaneously dehydrate

179 ne and a cationic rearrangement of the three-membered ring into a dimethoxypropylene isomer before di

180 l syn-pentane interactions which force a six-membered ring into a twist-boat conformation.

181 ed 4-thiazole substituents that form a seven-membered ring intramolecular hydrogen bond with a 5-posi

182 e derivative revealed the presence of a five-membered ring intramolecular hydrogen-bonding network.

183 with a high level of substitution on the six-membered ring is described.

184 otential for optical resolution of the seven-membered ring is discussed.

185 blished that the alpha-position of the three-membered ring is the favored deprotonation site.

186 for one of the complexes showed that the six-membered ring is very distorted and the thiophene ring i

187 highly diastereoselective synthesis of five-membered rings is achieved from the reaction of the corr

188 The formation of five-membered rings is against the Baldwin's rule.

189 he resulting bistetracene analogue with five-membered rings is comprehensively investigated by single

190 ation of the bistetracene analogue with five-membered rings is kinetically controlled while an "expec

191 trolled while an "expected" product with six-membered rings is thermodynamically more favored.

192 ble acyl-enzyme, which incorporates an eight-membered ring, is a covalent derivative of Ser70 linked

193 les of hydroacylation to form six- and seven-membered ring ketones require either embedded chelating

194 The five-membered ring lactam intermediates in these synthetic ro

195 Five- and six-membered ring lactams bearing aromatic, heteroaromatic,

196 much higher than those for carcinogenic four-membered ring lactones, resulting in the nitrosation of

197 hree-component reaction, giving rise to nine-membered-ring lactones.

198 lar cross-coupling to furnish the desired 30-membered ring macrocycle containing the critical (Z,Z,E)

199 ion of TMC647055 (10a), a nonzwitterionic 17-membered-ring macrocycle characterized by high affinity,

200 g metathesis reactions, generating 14- to 21-membered ring macrocyclic alkenes in 40-70% yield and 96

201 ps, leading to oxidative tailoring of the 16-membered ring macrolide antibiotic mycinamicin II in the

202 oward the synthesis of a suite of 12- and 14-membered ring macrolide natural products.

203 Notably, the 18-membered-ring moiety of pacritinib-a potent anti-cancer

204 emical structures around the ubiquitous five-membered ring motif, such as potentially therapeutic pro

205 The cis-isomers align in the main 12-membered ring (MR) channel of GME.

206 rom a strand in sequence, featuring up to 20-membered ring native chemical ligation transition states

207 dealing with the synthesis of five- and six-membered ring nitrogen containing heterocycles, then des

208 found to cyclize to give either five- or six-membered ring nitrogen heterocycles.

209 es has been tailored to bind the small, four-membered ring of oxetanocin-A over larger substrates.

210 ization procedures leading to the core seven-membered ring of the iboga skeleton, a cyclization that

211 this alkynylaldehyde, to construct the eight-membered ring of the target, unexpectedly provided a cyc

212 to compare the aromaticity in both the five-membered rings of 33, 34, 36 and 1,6-dioxa-6a-chalcopent

213 ains carried by the beta-lactam and the five-membered rings of the carbapenem core.

214 e and the centroids of three of the four six-membered rings of the pyrene system of a neighboring pyr

215 ly proposed "aromatic character" of the "two-membered rings" of the acetylene and butatriene molecule

216 ( summation operator) concentrations of 5/6-membered ring OH-PAHs in liver were smaller [mean of 931

217 open-cage fullerene, MMK-9, with an open 12-membered ring on its surface and silver(I) salts have be

218 ctions directed toward the syntheses of five-membered rings, other carbocycles and, finally, heterocy

219 modeling suggest that 7 was formed via a six-membered ring oxathiaphosphenine intermediate rather tha

220 nine intermediate rather than the usual four-membered ring oxathiaphosphetane of 2-6.

221 ophile attack for 2,3-trans-substituted five-membered ring oxocarbenium ions is strongly influenced b

222 Nucleophilic attack on seven-membered-ring oxocarbenium ions is generally highly ster

223 compared to that of reactions involving six-membered-ring oxocarbenium ions.

224 nicellin natural products from a number of 9-membered-ring precursors.

225 nce of oxygen, leads to formation of a seven-membered ring product, an overall [4+4-1] reaction.

226 der to generate the cis-double bond in seven-membered ring product, which reverses the selectivity.

227 ve a pair of diastereomeric heterocyclic six-membered ring products due to the newly formed sulfur ch

228 ruthenium-based system that affords the six-membered ring products was also developed.

229 Five- and six-membered ring products were obtained in good to excellen

230 ssed by PikAIII-TE and failed to generate 12-membered ring products.

231 ron-deficient alkenes and imines to form six-membered-ring products diastereoselectively.

232 The resulting seven-membered-ring products have three double bonds that coul

233 ): forming a five-membered ring versus a six-membered ring, respectively, thus exposing different car

234 ton acceptor is located in the five- and six-membered rings, respectively.

235 early 10(6)-fold between the five- and eight-membered ring series.

236 tendency for cations to occupy double eight-membered ring sites rather than single eight-membered ri

237 membered ring sites rather than single eight-membered ring sites.

238 splays a boat conformation for its Ge-Se six-membered ring ("six-ring"), while the previously known a

239 l groups and incorporating various (up to 28-membered) ring sizes.

240 ross-metathesis reactions, and a strained 14-membered ring stapled peptide by means of macrocyclic ri

241 s primarily high-energy dications with a six-membered-ring structure.

242 All chlorophylls have similar five-membered ring structures, with variations in the side ch

243 copodium alkaloid natural products share a 7-membered-ring substructure and may potentially arise fro

244 up abilities already established for the six-membered ring system (NHBn >> OH > NBn2), an N,N-dibenzy

245 molecular alkene hydroaminations forming six-membered ring systems are rare, especially for systems i

246 Both the natural cis and unnatural trans 6,6-membered ring systems proved accessible, with the latter

247 The reaction produces substituted five-membered ring systems stereoselectively and on preparati

248 ety of heterocyclic systems spanning small 3-membered ring systems to macroheterocycles.

249 3,5-triazinanes, leading to the five- or six-membered ring systems under mild conditions in yields up

250 re converted to trans-disubstituted 5- and 6-membered ring systems with perfect diastereoselectivity

251 strained by incorporation into six- or seven-membered ring systems, by addition of a lithiated primar

252 much more the pi-electron structure of five-membered rings than that of the six-membered ones.

253 ccess to biaryl sultams annulated into a six-membered ring that are otherwise difficult to obtain by

254 the enamine-iminium complex by forming a six-membered ring that favors one helicity of the electrocyc

255 ded one-dimensional lines of five- and eight-membered rings that are domain boundaries and stacking f

256 found with many of the oxygen-containing six-membered rings that were investigated.

257 new stereogenic center on the C2 of the five-membered ring, the reaction proceeds with formation of a

258 tively with the resonance energy of the five-membered ring; the nonaromatic cyclopentadiene derivativ

259 rahedra bridged through hydroxide into three-membered rings; these units link together to produce sev

260 and three-component domino reaction of four-membered ring thionation reagents such as 2,4-bis(4-meth

261 3]rotaxane consisting of two coordinating 30-membered rings threaded by a two-binding-site axis has b

262 he diastereoselective formation of the seven-membered ring through a Friedel-Crafts triflation and a

263 are accompanied by contraction of the seven-membered ring to give the corresponding substituted 1-di

264 Most notable is the reluctancy of these four-membered rings to form the corresponding N-heterocyclic

265 ompetition reactions showed that these seven-membered ring trans-alkenes underwent [4+2] cycloadditio

266 Seven-membered-ring trans-alkenes undergo rapid, uncatalyzed c

267 undergo additions to aldehydes to form seven-membered-ring trans-alkenes with high diastereoselectivi

268 A twelve-membered ring transition state was found only without ap

269 the ribosome would proceed through an eight-membered ring transition state, involving a proton shutt

270 oncerted mechanisms of four-, six- and eight-membered ring transition states, and a stepwise mechanis

271 es have been elaborated from a panel of five-membered ring trifluoromethylated amino acids (Tfm-AAs)

272 h the first solvation shell, show that the 8-membered ring TS renders values in better agreement with

273 Also, ITQ-49 contains double four-membered-ring units where Ge is preferentially located,

274 he tert-butyl and p-xylyl groups in the five-membered-ring upper half may be introduced simultaneousl

275 r comprises a fluorene lower half and a five-membered-ring upper half; the upper-half ring is fused t

276 trate to Fe(2+)versus Ni(2+): forming a five-membered ring versus a six-membered ring, respectively,

277 l lineNH and cis-1,3-butadiene to form a six-membered ring was examined by quantum calculations.

278 The influence of four-membered ring was examined using spectroscopy, crystallo

279 The challenging 11-membered ring was forged via a diastereoselective thioni

280 red to one where it was tethered by an eight-membered ring was less than 100-fold, suggesting that fu

281 almost planar N-arylamine and a planar four-membered ring, was revealed by both AM1 calculations and

282 ,5-disubstituted indole derivatives having 6-membered rings were designed, synthesized, and demonstra

283 es ranging in size from twelve- to seventeen-membered rings were synthesized in moderate to high yiel

284 d nitrogen heterocycle is replaced by a 9-12-membered ring, were made by an unactivated Smiles rearra

285 overlapping plus the ring strain of the five-membered ring, whereas steric effects seem to be unimpor

286 ization of 6pi-electrons over the BC2N2 five-membered ring, which thus indicates the aromatic propert

287 distinct local structures, situated in the 8 membered ring windows of the side pockets.

288 connected to each other through small eight-membered-ring windows, resulting in a unidirectional sma

289 s relatively little interaction of the eight-membered ring with active site residues.

290 PF3)3(2-) forms the first example of a three-membered ring with all the vertices constituted by penta

291 ng a terminal alkyne led to the desired five-membered ring with high enantioselectivities (up to 91%

292 pectra suggest FeL2(6-) likely forms 5- or 7-membered rings with CDX and olaquindox through the N and

293 ion was developed for the synthesis of seven-membered rings with diverse functionalities.

294 a benzofused saturated heterocyclic 5- or 6-membered ring, with an additional vicinal amino stereoce

295 the enantioselective construction of 3- to 6-membered rings, with a particular focus on 5-membered ri

296 yclization reaction, forming a bridged seven-membered ring within a polycyclic system.

297 of natural origin is a 1,2-trans fusion of 5-membered rings within a [3.3.0]-bicycle, a motif present

298 can selectively react with HCys to form a 6-membered ring without the addition of nucleophiles.

299 disubstituted alkenes to form seven- and six-membered rings without requiring substrate-embedded chel

300 ine derivative salts with fused five and six-membered rings (X-ray) were obtained via modification of