Kari Lappalainen

Interaction of anisole with 3α-hydroxy-5β-cholan-24-oic acid macrolides. Part 1. Comparative 1H NMR spectral investigation

Abstract 1 H NMR spectral investigation on the interaction of anisole (methoxybenzene) with five different (varying by ring size and substitution) cyclic 3α-hydroxy-5β-cholan-24-oic acid macrolides were performed. For 3α-hydroxy-5β-cholan-24-oic acid (lithocholic acid) macrolides (from triolide to pentolide) no effect was observed. In contrast, for 7α-trifluoroacetyloxy (7α-TFA) substituted lithocholate triolide obtained from chenodeoxycholic acid and for 12α-trifluoroacetyloxy (12α-TFA) substituted lithocholate triolide obtained from deoxycholic acid, clear site specific effects were observed. In the case of the 7α-TFA derivative, the aromatic guest causes the strongest up-field shift on the angular methyl 19 at the A/B ring junction of the steroid unit, and in 12α-TFA isomer the strongest effect is directed at the angular methyl 18 located at the C/D ring junction of the steroid skeleton. These findings are discussed in terms of steric factors and the size and flexibility of the cavity of the host molecule. Molecular mechanics is used in modeling the structures of three triolides.

13C NMR Spectral Identification of Four Cyclolithocholates (3α–Hydroxy–5β–cholan–24–oate Macrolides)

Four macrolides (ranging from dimer to pentamer) of lithocholic (3α‐hydroxy‐5β‐cholan‐24‐oic) acid were identified by electron impact and fast atom bombardment mass spectrometry and 13C NMR spectrometry. The 13C NMR chemical shift assignments are based on comparison with related monomeric species and DEPT experiments.

13C NMR spectral assignments of 3α,3′α‐bis(arylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters: new lithocholic acid‐based molecular clefts

3α,3′α‐Bis(arylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters (1–3) were synthesized by the reaction of an aroyl chloride (aroyl=2,6‐dichlorobenzoyl, 2‐naphthoyl and 1‐pyrenoyl) with lithocholic acid (3α‐hydroxy‐5β‐cholan‐24‐oic acid) ethane‐1,2‐diol diester. The 13C NMR chemical shift assignments of the formed molecular clefts 1–3, pyrene‐1‐carboxylic acid methyl ester (4) (used as model compound) and 1‐pyrenoyl chloride (5) are based on literature data and 13C DEPT‐135, 1H,13C HMQC and 1H,13C HMBC experiments. The molecular weights of 1–3 were determined by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Copyright

13C and 15N NMR chemical shift assignments of N-1-(2- azidoethyl)-4-R-pyrimidin-2-ones by 1H,X HMQ(B)C with z-gradient selection

13C and 15N NMR chemical shift assignments based on z‐gradient selected 1H,X (X=13C and 15N) HMQC and HMBC experiments are reported for N‐1‐(2‐azidoethyl)pyrimidin‐2‐one (ring system of cytosine), its five 4‐R derivatives [where R=NH2, OCH3, N(CH2)4, NHCH2CH(CH3)2 and N(CH3)2] and 2‐azidoethyl tosylate. The possibilities of detecting all nitrogens in these molecules containing (i) an azido group at N‐1 and (ii) an electronegative substituent at C‐4 are limited. First, the terminal nitrogen of the azido group is difficult to observe because the nearest proton (in a CH2 group) is located four bonds away from it. Second, in contrast to N‐1, N‐3 in N‐1‐(2‐azido‐ethyl)‐4‐pyrimidin‐2‐ones remained undetected. For that reason, an unsubstituted derivative (R=H) was also prepared, where N‐3 was easily observed.

17O NMR chemical shifts of 3-(substituted methylene)-(Z)-1(3H)-isobenzofuranones: correlations with IR stretching wavenumbers and AM1 charges

17O NMR chemical shifts were determined for 1(3H)‐isobenzofuranone, its 3‐methylene‐ and 3‐(Z)‐(methylmethylene) derivatives and a series of 3‐aryl‐, 3‐aryloxy‐ and 3‐arylthiomethylene‐(Z)‐1(3H)‐isobenzofuranones. The observed δ(17O) values of the C=O‐group of the furanone moiety in the arylidene series show significant linear dependences on the wavenumber of the IR stretching vibration, ν(CO), the AM1 charge density at the double bond oxygen, q(O), and the Hammett σ+ constant of the substituent in the phenyl ring. These findings suggest that the substituent effects are efficiently transmitted from the phenyl ring to the C=O group via the conjugated double bond system of the 3‐arylidene‐(Z)‐1(3H)‐isobenzofuranone. In the case of aryloxy and arylthio derivatives these correlations were less significant than in arylidene compounds, reflecting the diverse effects of the heteroatoms (O or S) on the transmission mechanism.