ライフサイエンスコーパス: bridgehead

1 substitution at a methylene attached to the bridgehead (1-) position of the 2-azabicyclo[2.1.1]hexan

2 )N) bridgehead with an ethano (NCH(2)CH(2)N) bridgehead affects the conformational equilibrium of the

3 nantholactams were formed by stereoselective bridgehead alkene reduction, a process that transfers st

4 ic system of the taxane family, containing a bridgehead alkene, is forged via a vicinal difunctionali

5 e addition of phenylchlorocarbene (PhCCl) to bridgehead alkenes adamantene and homoadamantene, respec

6 The exclusive product in each case was the bridgehead alkyl chloride formed by fragmentation of the

7 he steric effects of the substituents at the bridgehead allows for the precise control of the directi

8 transannular cyclization and reduction of a bridgehead alpha-chloro amine functionality produces the

9 ates are multiply functionalized and carry a bridgehead alpha-ketol array which was key to isomerizat

10 The ring size, bridgehead amino acid chirality, and side-chain amide bo

11 nvolves cleavage of the C-C bond between the bridgehead and one carbonyl atom, C(bridge)-C(O), yieldi

12 Two new classes of agonists in which the bridgehead anilino group from our first series was repla

13 oming a significant drawback of our original bridgehead anilino-substituted series.

14 conserved lysine and cysteine residues, the bridgehead atom of the dithiolate ligand, or the reduced

15 direct control of the stereochemistry of the bridgehead atoms of the fused ring using new MDOs self-a

16 he substitution of positions adjacent to the bridgeheads atoms which would otherwise be vulnerable to

17 The larger slope is due to the smaller bridgehead-bridgehead distance in the bicyclopentane rin

18 The fragmentation reaction for bridgehead-bromine-substituted derivatives was much fast

19 The installation of bridgehead bulk in the -SCH2CR2CH2S- dithiolate (R = Me,

20 mbined in a thermodynamic cycle to provide a bridgehead C-H bond dissociation energy (BDE) of 109.7 +

21 Bridgehead C-H bond dissociation enthalpies of 105.7 +/-

22 rearrangements were employed in building the bridgehead (C20) and the spiroanilide (C7) quaternary ce

23 order of increasing strain in the resulting bridgehead carbocation, but the range of rate constants

24 cene, such that the bulky methyl-substituted bridgehead carbon atoms are attached to C2 and C3 of the

25 ptor are attached via alkyne linkages to the bridgehead carbon atoms of bicyclo[2.2.2]octane and all

26 bridged, have methyl groups adjacent to the bridgehead carbon atoms, and have aryl substituents prot

27 , and proximity of the forming olefin to the bridgehead carbon of the bicyclic affect the efficiency

28 Epimerization of the 7'a bridgehead carbon under acidic conditions was observed f

29 ubstituent rather than a methyl group at the bridgehead carbon.

30 y from the bridgehead lactam nitrogen to the bridgehead carbon.

31 The geometry of the bridgehead carbons made S(N)2 reactions impossible.

32 he trans-dimethyl geometry of the quaternary bridgehead carbons via a reductive cyclization.

33 carrying various functionality at one of the bridgehead carbons, have been accomplished.

34 The results also show that a change in the bridgehead chirality of the 5.6.5 scaffold brings about

35 analogues with different bridge lengths and bridgehead chirality.

36 (1,1'-5) bridge length (21 and 22 atoms) and bridgehead configuration, we may hypothesize that they a

37 first bridgehead sultams and the only known bridgehead disulfonimide are described.

38 s if the second step requires formation of a bridgehead double bond.

39 nes, compounds having exceptionally strained bridgehead double bonds.

40 ation reactions, including the generation of bridgehead enolates, thus enabling the total synthesis o

41 for assembly of the ethyl side chain at C6, bridgehead epimerization at C5, installation of the C2-t

42 Additionally, we found evidence of one bridgehead event: a likely Eastern US source for the cen

43 or quantification of the deformations of the bridgehead functionalities and provided a strategy for t

44 ptycenes bearing H (1-H) or Bu (1-Bu) at the bridgeheads gave triptycenes with triphenylene blades.

45 nt geometry with two phosphorus atoms at the bridgehead has been synthesized.

46 product, the propargylic substituent and the bridgehead hydrogen are cis with respect to each other o

47 n the allylic hydroxyl group is trans to the bridgehead hydrogen are found to be the electrostatic in

48 The loss of the bridgehead hydrogen from the (3S,5S)-carbapenam during t

49 nal modifications to 14 also showed that the bridgehead hydroxyl group could be replaced with a propi

50 The tandem reaction proceeds through a bridgehead iminium ion, a functionality that has rarely

51 is further suggested that the nature of the bridgehead in the dithiolate ligand can exert a stereoel

52 yclic systems with a nitrogen 10 atom at the bridgehead, including indolizidines and quinolizidines,

53 cess that transfers stereochemistry from the bridgehead lactam nitrogen to the bridgehead carbon.

54 But the amide groups of bicyclic bridgehead lactams are highly twisted, and this distorti

55 nds (with bond angle 94 degrees ) and the C2 bridgehead leading to anti-endo elimination of the C1-me

56 ee of strain-induced pyramidalization at the bridgehead nitrogen and twist about the amide bond, but

57 Tricyclic systems with quaternary bridgehead nitrogen atoms are rare but an interesting cl

58 Since substitution at bridge and bridgehead nitrogen atoms can be easily introduced, 1,4,

59 o bicyclic heterocyclic scaffolds containing bridgehead nitrogen centers.

60 is investigated, and a dominant role of the bridgehead nitrogen in reducing the amount of partially

61 t time various heteroaromatic compounds with bridgehead nitrogen, including indolizines, bispyrrolopy

62 bonded network involving the bridge and both bridgehead nitrogens, producing a difference of more tha

63 ci was shown to incorporate one label at the bridgehead of (3S,5S)-carbapenam carboxylic acid, but no

64 n of structural distortions of the nonplanar bridgehead olefin and lactam functionalities in 1,2-diaz

65 The reactivity of the strained, bridgehead olefin of this secondary metabolite with biol

66 Twisted amides containing nitrogen at the bridgehead position are attractive practical prototypes

67 In addition, an amino group at the fourth bridgehead position provides a flexible linker for attac

68 on quadricyclane lability, substitution at a bridgehead position with a methyl group produced a quadr

69 ent in the formation of an sp(2) carbon at a bridgehead position.

70 ition of the nitrogen of 4-quinolones to the bridgehead position.

71 eta, H11alpha (1S,11R) configurations at the bridgehead positions of 22 were established by means of

72 er coupling is observed to the unique B-CH-B bridgehead proton (a((1)H) = 7.2 +/- 0.2 G) and to eight

73 stituted-6-azabicyclo[3.2.1]octanes with two bridgehead quarternary carbon centers is reported.

74 g the same peripheral substituents but other bridgehead residues failed.

75 H(1-29)-NH2, where Xaa and Yaa represent the bridgehead residues of a side-chain cystine or [i-(i + 4

76 mical shifts, and charge distribution in the bridgehead silylium ions are discussed and compared.

77 hydronium and hydroxide ions at 3-coordinate bridgehead sites.

78 This includes examples containing a bridgehead sp(3) quaternary carbon center as well as the

79 Optimization of the bridgehead substituent led to propionic acid 29 (BG9928)

80 arbon atom and demonstrates the influence of bridgehead substituents and bridging rings on planarity.

81 with results calculated with neglect of the bridgehead substituents for all of the chemical shifts b

82 eaking of bonds was studied by investigating bridgehead substitution in 1,3-di-tert-butylbicyclo[1.1.

83 Bridgehead substitution leads to a lengthening of the ce

84 A convergent strategy has allowed access to bridgehead sultam 9 and the related carboxamides 10 and

85 for accomplishing the ring contraction of a bridgehead sultam.

86 Syntheses of the first bridgehead sultams and the only known bridgehead disulfo

87 The 1,3-adamantanediyl dication 1b with two bridgehead tertiary carbocationic centers was found to b

88 With a NCH(2)CH(2)N bridgehead, the phenyl and the cyclohexyl esters prefer

89 e out conformation, whereas with the NCH(2)N bridgehead, they were found to prefer the folded conform

90 ngth of alkyl substituents at the triptycene bridgeheads to the reaction have been performed, reveali

91 which the Bu groups fill the voids near the bridgehead, was crystalline.

92 al along with the substituent at position-1 (bridgehead) which force attack of the lithium reagent fr

93 Replacing the methano (NCH(2)N) bridgehead with an ethano (NCH(2)CH(2)N) bridgehead affe