Synthetic studies on glycosphingolipids from protostomia phyla: synthesis of neogala-series glycolipid analogues containing a mannose residue from the earthworm Pheretima hilgendorfi.

Two kinds of glycosphingolipid analogues from the earthworm Pheretima hilgendorfi were synthesized as follows: the trisaccharide 2-(tetradecyl)hexadecyl alpha-D-mannopyranosyl-(1-->4)-beta-D-galactopyranosyl-(1-->6)-beta-D- galactopyranoside (13) and the tetrasaccharide 2-(tetradecyl) hexadecyl alpha-D-galactopyranosyl-(1-->6)-[alpha-D-mannopyranosyl-(1-->4)]-beta-D - galactopyranosyl-(1-->6)-beta-D-galactopyranoside (20) were synthesized by stepwise condensation of suitably protected monosaccharide units. A 2-(trimethylsilyl)ethyl 2,3,4-tri-O-benzoyl-beta-D-galactopyranoside derivative (5) was used as the glycosyl acceptor and thiophenyl derivatives of D-galactose and D-mannose were used as donors respectively.     

Synthesis, inhibitory effects on nitric oxide and structure-activity relationships of a glycosphingolipid from the marine sponge Aplysinella rhax and its analogues

The novel glycosphingolipid, β-D-GalNAcp(1-->4)[α-D-Fucp(1-->3)]-β-D-GlcNAcp(1-->)Cer (A), isolated from the marine sponge Aplysinella rhax has a unique structure, with D-fucose and N-acetyl-D-galactosamine moieties attached to a reducing-end N-acetyl-D-glucosamine through an α1-->3 and β1-->4 linkage, respectively. We synthesized glycolipid 1 and some non-natural di- and trisaccharide analogues 2-6 containing a D-fucose residue. Among these compounds, the natural type showed the most potent nitric oxide (NO) production inhibitory activity against LPS-induced J774.1 cells. Our results indicate that both the presence of a D-Fucα1-3GlcNAc-linkage and the ceramide aglycon portion are crucial for optimal NO inhibition.     

Synthetic studies on glycosphingolipids from Protostomia phyla: synthesis of amphoteric glycolipid analogues containing a phosphocholine residue from the earthworm Pheretima hilgendorfi.

Two kinds of amphoteric glycosphingolipid analogues from the earthworm Pheretima hilgendorfi were synthesized as follows: The key reaction is a coupling of a phosphocholine group at the position C-6 of 1 and 6 which was attempted using 2-chloro-2-oxo-1,3,2-dioxaphospholane, followed by reaction of the resulting cyclic phosphate intermediate with anhydrous trimethylamine to give 2 and 7. Subsequent debenzylation afforded target compounds (3, 8). Their ability to inhibit the histamine release in vitro was examined.     

Rossicasins A, B and rosicaside F, three new phenylpropanoid glycosides from Boschniakia rossica

Three phenylpropanoid glycosides have been isolated, together with the known phenylpropanoid glycosides rossicaside A (4), B (5), E (6), and trans-p-coumaryl alcohol 1-O-beta-D-glucopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-->3)-beta-D-glucopyranoside (7), and an acylated oligosaccharide beta-D-glucopyranosyl(1-->4)-alpha-L-rhamnopyranosyl-(1-->3)-(4-O-trans-caffeoyl)-D-glucopyranose) (8), from the aqueous extract of Boschniakia rossica (CHAM. et SCHLECH.) FEDTSCH. et FLEROV. Spectroscopic evidence led to the assignments of their structures as trans-p-coumaryl-(6'-O-beta-D-xylopyranosyl)-O-beta-D-glucopyranoside (1), trans-p-coumaryl-(6'-O-alpha-L-arabinopyranosyl)-O-beta-D-glucopyranoside (2) and 2-(3,4-dihydroxyphenyl)-R,S-2-ethoxy-ethyl-O-beta-D-glucopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-->3)(4-O-trans-caffeoyl)-beta-D-glucopyranoside (3), designated as rossicasin A, rossicasin B, and rossicaside F, respectively. Compound 7 was identified from the degradation reaction and this is the first isolation from a natural source.     

Glycolipids from sponges. 20. J-Coupling analysis for stereochemical assignments in furanosides: structure elucidation of vesparioside B, a glycosphingolipid from the marine sponge Spheciospongia vesparia

Reinvestigation of the glycosphingolipid composition of the marine sponge Spheciospongia vesparia revealed the presence of vesparioside B ( 2a), a new furanose-rich hexaglycosylated glycosphingolipid that is the most complex glycosphingolipid isolated from a marine sponge to date. The structure of the new compound was elucidated using extensive 2D NMR studies and chemical degradation. Particularly useful for structure elucidation of vesparioside B was a quantum mechanical computational study, showing that in furanosides a vicinal coupling constant <2.0 Hz (for H-1/H-2 or H-3/H-4) or <3.5 Hz (for H-2/H-3) is a proof of the trans orientation of the relevant protons. This general rule, combined with ROE data, allowed us to elucidate the relative stereochemistry (including anomeric configuration) of the three furanose five-membered rings.     

A new leishmanicidal saponin from Brunfelsia grandiflora

A new furostan-type saponin (1) was isolated from the methanolic extract of Brunfelsia grandiflora leaves, together with four known compounds. The chemical structure of 1 was determined by spectroscopic analysis and chemical reaction to be 26-O-beta-D-glucopyranosyl 22alpha-methoxyfurost-3beta,26-diol 3-O-beta-D-xylopyranosyl(1-->3)-{beta-D-glucopyranosyl(1-->2)}-beta-D-glucopyranosyl(1-->4)-beta-D-glucopyranoside. Compound 1 showed potent leishmanicidal activity in vitro against Leishmania major.     

Glycosides from Bougainvillea glabra

Three glycosides were isolated from Bougainvillea glabra and their structures were determined by extensive use of 1D and 2D NMR spectroscopy ((1)H and (13)C). First compound was identical to momordin IIc (quinoside D) [beta-D-glucopyranosyl 3-O-[beta-D-xylopyranosyl-(1 --> 3)-O-(beta-D-glucopyranosyluronic acid)] oleanolate], second compound was quercetin 3-O-alpha-L-(rhamnopyranosyl)(1 --> 6)-[alpha-L-rhamnopy-ranosyl(1 --> 2)]-beta-D-galactopyranoside and third compound was its derivative quercetin 3-O-alpha-L-(4-caffeoylrhamnopyranosyl)(1 --> 6)-[alpha-L-rhamnopyranosyl (1 --> 2)]-beta-D-galactopyranoside, a new natural product.     

Synthesis of a new glycosphingolipid from the marine ascidian Microcosmus sulcatus using a one-pot glycosylation strategy

A novel neutral glycosphingolipid found in Microcosmus sulcatus containing a β-d-Galp(1→4)[α-d-Fucp-(1→3)]β-d-Glcp-(1→)Cer motif was synthesized. Trisaccharide derivatives were synthesized using trimethylsilyltrifluoromethanesulfanate (TMSOTf) and N-iodosuccimide (NIS)/trifluoromethane sulfonic acid (TfOH) as the promoters. Synthesis was achieved with an efficient one-pot glycosylation strategy. This is the first report of a one-pot glycosylation strategy using the procedure of Boons et al. for the synthesis of a natural product. Coupling of trisaccharide derivative 19 and ceramide derivative 20 by TMSOTf afforded the glycosphingolipid derivative 21. The fully protected glycoside was deprotected to give the target glycosphingolipid 2.     

Triterpene glycosides from the stems of Akebia quinata

The stems of Akebia quinata have been analyzed for their triterpene glycoside constituents, resulting in the isolation of six new triterpene glycosides, along with 19 known ones. On the basis of extensive spectroscopic analysis, including 2D NMR data, and chemical evidence, the structures of the new compounds were deter-mined to be 3beta-[(O-beta-D-glucuronopyranosyl-(1-->3)-alpha-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3beta-[(O-beta-D-glucuronopyranosyl-(1-->3)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]olean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3beta-[(O-beta-D-glucuronopyranosyl-(1-->3)-alpha-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3beta-[(O-beta-D-glucuronopyranosyl-(1-->3)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-23-hydroxyolean-12-en-28-oic acid O-alpha-L-rhamnopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3beta-[(O-beta-D-glucopyranosyl-(1-->3)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-29-hydroxyolean-12-en-28-oic acid, and 3beta-[(O-beta-D-glucopyranosyl-(1-->3)-O-[alpha-L-rhamnopyranosyl-(1-->2)]-alpha-L-arabinopyranosyl)oxy]-23,29-dihydroxyolean-12-en-28-oic acid, respectively. The main triterpene glycosides contained in the stems of A. quinata were found to have two sugar units at C-3 and C-28 of the aglycone in this study, whereas those of Akebia trifoliate were reported to possess one sugar unit at C-28 of the aglycone. It may be possible to distinguish between A. quinata and A. trifoliate chemically by comparing their triterpene glycoside constituents.     

Three cycloartane glycosides from Cimicifuga rhizome and their immunosuppressive activities in mouse allogeneic mixed lymphocyte reaction

One known (1) and two new cycloartane triglycosides, 20S,22R,23S,24R-16beta,23;22,25-diepoxy-cycloartane-3beta,23,24-triol 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->2)-beta-D-xylopyranoside (2) and 20S,22R,23S,24R-16beta,23;22,25-diepoxy-cycloartane-3beta,23,24-triol 3-O-(6-O-trans-isoferuloyl-beta-D-glucopyranosyl)-(1-->2)-beta-D-glucopyranosyl-(1-->2)-beta-D-xylopyranoside (3), were isolated from a commercial Cimicifuga Rhizome. Their structures were determined by two dimensional (2D) NMR spectroscopic analysis and chemical evidence. These compounds suppressed the proliferation of lymphocytes in mouse allogeneic mixed lymphocyte reaction.     

Synthetic studies on glycosphingolipids from protostomia phyla: synthesis of a glycosphingolipid analogue from the parasite Spirometra erinacei

Novel neutral glycosphingolipids isolated from the plerocercoids of a tapeworm, Spirometra erinacei, may be expected to be involved in host-parasite interactions. We have synthesized this glycosphingolipid analogue containing 2-branched fatty alkyl residue in place of ceramide. Glycosylation of nonreducing-end trisaccharide derivative 15 with the reducing-end disaccharide derivative 17 in the presence of trimethylsilyl triflate (TMSOTf) gave the desired oligosaccharide derivative in good yield. The fully per-O-acylated 2-(trimethylsilyl)ethyl glycoside 19 was converted to glycosylimidate 20, which was condensed with 2-(tetradecyl)hexadecanol and subsequently deacylated to give the target glycosphingolipid analogue 22.     

Five new bidesmoside triterpenoid saponins from Stauntonia chinensis

Eleven triterpenoid saponins (1-11) were isolated from Stauntonia chinensis DC. (Lardizabalaceae), including five new compounds, yemuoside YM(21-25) (1-3, 6, 7) structures of which were elucidated by chemical methods and a combination of MS, 1D- and 2D- NMR experiments including DEPT, (1)H--(1)H COSY, HSQC, HMBC, TOCSY, and NOESY as 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-rhamnopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonicacid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (1), 3-O-beta-D-xylopyranosyl-(1 --> 3)-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranosyl-akebonic acid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (2), 3-O-beta-D-glucopyranosyl-(1 --> 3)-alpha-L-arabinopyranosyl-akebonic acid-28-O-alpha-L-rhamnopyranosyl-(1 --> 4)-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (3), 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-rhamnopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonic acid-28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (6), 3-O-alpha-L-arabinopyranosyl-(1 --> 3)-[alpha-L-arabinopyranosyl-(1 --> 2)-]alpha-L-arabinopyranosyl-akebonic acid-28-O-beta-D-glucopyranosyl-(1 --> 6)-beta-D-glucopyranosyl ester (7).     

The mechanisms of the reactions of W and W+ with COx (x=1, 2): a computational study

The mechanisms of the reactions of W and W+ with COx (x=1, 2) were studied at the CCSD(T)/[SDD+6-311G(d)]//B3LYP/[SDD+6-31G(d)] level of theory. It was shown that the gas-phase reaction of W with CO2 proceeds with a negligible barrier via an insertion pathway, W(7S)+CO2(1A1)-->W(eta2-OCO)(6A')-->OW(eta1-CO)(1A)-->WO (3Sigma+)+CO(1Sigma). This oxidation process is calculated to be exothermic by 32.4 kcal/mol. Possible intermediates of this reaction are the W(eta2-OCO) and OWCO complexes, among which the latter is 37.4 kcal/mol more stable and lies 39.7 and 7.3 kcal/mol lower than the reactants, W(7S)+CO2(1A1), and the products, WO (3Sigma+)+CO(1Sigma), respectively. The barrier separating W(eta2-OCO) from OWCO is 8.0 kcal/mol (relative to the W(eta2-OCO) complex), which may be characterized as a W+delta-(CO2)-delta charge-transfer complex. Ionization of W does not change the character of the reaction of W with CO2: the reaction of W+ with CO2, like its neutral analog, proceeds via an insertion pathway and leads to oxidation of the W-center. The overall reaction W+(6D) + CO2(1A1)-->W(eta1-OCO)+(6A)-->OW(eta1-CO)+(4A)-->WO+(4Sigma+)+CO(1Sigma) is calculated to be exothermic by 25.4 kcal/mol. The cationic reaction proceeds with a somewhat large (9.9 kcal/mol) barrier and produces two intermediates, W(eta1-OCO)+(6A) and OW(eta1-CO)+(4A). Intermediate W(eta1-OCO)+(6A) is 20.0 kcal/mol less stable than OW(eta1-CO)+(4A), and separated from the latter by a 35.2 kcal/mol barrier. Complex W(eta1-OCO)+(6A) is characterized as an ion-molecular complex type of W+-(CO2). Gas-phase reactions of M=W/W+ with CO lead to the formation of a W-carbonyl complex M(eta1-CO) for both M=W and W+. The C-O insertion product, OMC, lies by 5.2 and 69.3 kcal/mol higher than the corresponding M(eta1-CO) isomer, for M=W and W+, respectively, and is separated from the latter by a large energy barrier.     

Steroidal glycosides and aromatic compounds from Smilax riparia

Two new steroidal glycosides named riparosides A (1) and B (2), and two aromatic compounds (3, 4), together with four known flavonoid derivatives have been isolated from the EtOH extract of the rhizomes and roots of Smilax riparia A. DC. The structure of riparoside A (1) was determined to be 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-glucopyranosyl 3beta,20alpha-dihydroxy-5alpha-furost-22(23)-ene 26-O-beta-D-glucopyranoside. Riparoside B (2) was characterized as 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-glucopyranosyl 3beta,16beta-dihydroxy-5alpha-pregnan-20-one 16-O-[5-O-beta-D-glucopyranosyl 5-hydroxy-4-methyl-pentanoic acid]-ester 26-O-beta-D-glucopyranoside. Compounds 3 and 4 were elucidated as a sucrosyl ferulic acid ester and 7-O-methyl-10-oxythymol gentiobioside, respectively.     

Straightforward synthesis of thiodisaccharides by ring-opening of sugar epoxides

3,4-Anhydro hexopyranosides have been prepared by diastereoselective epoxidation of derivatives of 2-propyl 3,4-dideoxy-alpha-D-erythro-hex-3-enopyranoside (5), selectively protected at HO-2 and HO-6. The allylic group at C-2, in 5 and derivatives, plays a critical role in the facial selectivity of the epoxidation reaction. Thus, the free HO-2 in 3 (the 6-O-acetyl derivative of 5) directs the attack of m-chloroperbenzoic acid from the more hindered alpha face of the molecule to give 2-propyl 6-O-acetyl-3,4-anhydro-alpha-D-allopyranoside (7) accompanied by the beta epoxide 6 as a very minor product. Reverse diastereoselectivity has been obtained when the HO-2 in 3 was substituted by a bulky tert-butyldimethylsilyl (TBS) group. In this case, the major isomer was the 2-O-TBS derivative of 6 (alpha-D-galacto configuration). The ring-opening of sugar epoxides by nucleophilic per-O-acetyl-1-thio-beta-D-glucopyranose (11) was employed as a convenient approach to the synthesis of (1-->3)- and (1-->4)-thiodisaccharides. For example, ring-opening of the oxirane 7 by 11 led to the expected regioisomeric per-O-acetyl thiodisaccharides beta-D-Glc-S-(1-->3)-4-thio-alpha-D-Glc-O-iPr (12) and beta-D-Glc-S-(1-->4)-4-thio-alpha-D-Gul-O-iPr (13). Regioselectivity in the construction of the (1-->4)-thioglycosidic linkage could be achieved by hindering C-3 of the 3,4-anhydro sugar with a bulky silyloxy group at the vicinal C-2. For instance, coupling of the 2-O-TBS derivative of 7 with 11 led regioselectively to the protected thiodisaccharide beta-D-Glc-S-(1-->4)-4-thio-alpha-D-Glc-O-iPr (27). The utility of the approach was demonstrated through the synthesis of sulfur-linked analogues of naturally occurring (laminarabiose and cellobiose) and non-natural disaccharides (i.e., beta-D-Glc-(1-->4)-alpha-D-Gul).     

Norlanostane and lanostane glycosides from the bulbs of Chionodoxa luciliae and their cytotoxic activity

Ten lanostane glycosides (1-10), including two new norlanostane glycosides (2 and 7) and a new lanostane glycoside with a spirolactone ring system (9), were isolated from the fresh bulbs of Chionodoxa luciliae (Liliaceae). The structures of the new compounds were determined on the basis of extensive spectroscopic analysis and the results of hydrolytic cleavage to be (23S)-3beta-[(O-beta-D-apiofuranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranosyl)oxy]-17alpha,23-epoxy-28,29-dihydroxy-27-norlanost-8-en-24-one (2), (23S)-17alpha,23-epoxy-29-hydroxy-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranosyl)oxy]-27-norlanost-8-ene-15,24-dione (7), and (23S,25R)-17alpha,23-epoxy-29-hydroxy-3beta-[(O-alpha-L-rhamnopyranosyl-(1-->2)-O-[beta-D-glucopyranosyl-(1-->3)]-O-beta-D-glucopyranosyl-(1-->2)-alpha-L-arabinopyranosyl-(1-->6)-beta-D-glucopyranosyl)oxy]lanost-8-en-23,26-olide (9), respectively. The cytotoxic activity of the isolated compounds against HSC-2 human oral squamous cell carcinoma cells are also reported.     

Four new triterpene glycosides from Nigella damascena

Four new triterpene glycosides, named nigellosides A, B, C, and D, were from the air-dried aerial parts of Nigella damascena L. (Ranunculaceae), and the structures were elucidated on the basis of spectroscopic data including 2D NMR spectra and chemical evidence. Their chemical structures have been characterized as 3-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl gypsogenin 28-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranosyl gypsogenin 28-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl hederagenin 28-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, and 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl hederagenin 28-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester.     

Four new oleanane saponins from Anemone anhuiensis

Four new oleanane triterpene saponins, anhuienosides C-F, together with three known saponins, were isolated from the rhizomes of Anemone anhuiensis (Ranunculaceae). The structures of anhuienosides C-F were elucidated as 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl oleanolic acid 28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3-O-beta-D-xylopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, 3-O-beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-xylopyranosyl oleanolic acid 28-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester, respectively.     

Theoretical study of the reaction mechanism of HCN+ and CH4 of relevance to Titan's ion chemistry

Titan is the largest satellite of Saturn. In its atmosphere, CH4 is the most abundant neutral after nitrogen. In this paper, the complex doublet potential-energy surface related to the reaction between HCN+ and CH4 is investigated at the B3LYP/6-311G(d,p), CCSD(T)/6-311G++(3df,2pd)(single-point), and QCISD/6-311G(d,p) computational levels. A total of seven products are located on the PES. The initial association of HCN+ with CH4 is found to be a prereaction complex 1 (HCNHCH3(+)) without barrier. Starting from 1, the most feasible pathway is the direct H-abstraction process (the internal C-H bond dissociation) leading to the product P1 (HCNH++CH3). By C-C addition, prereaction complex 1 can form intermediate 2 (HNCHCH3(+)) and then lead to the product P2 (CH3CNH++H). The rate-controlling step of this process is only 25.6 kcal/mol. It makes the Path P2 (1) R --> 1 --> TS1/2 --> 2 --> TS2/P2 --> P2 another possible way for the reaction. P3 (HCNCH3(+) + H), P5 (cNCHCH2(+) + H2), and P6 (NCCH3(+) + H2) are exothermic products, but they have higher barriers (more than 40.0 kcal/mol); P4 (H + HCN + CH3(+)) and P7 (H + H2 + HCCNH+) are endothermic products. They should be discovered under different experimental or interstellar conditions. The present study may be helpful for investigating the analogous ion-molecule reaction in Titan's atmosphere.     

Five new phenylethanoid glycosides from the whole plants of Lamium purpureum L

Five new phenylethanoid glycosides, lamiusides A (1), B (2), C (3), D (4) and E (5), were isolated from the whole plants of Lamium purpureum L. (Labiatae) together with seven known compounds (6-12). On the basis of chemical and spectral analyses, the structures of the new compounds were elucidated to be 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-galactopyranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->3)-(4-O-trans-caffeoyl)-beta-D-glucopyranoside (1), 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-galactopyranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->3)-(4-O-trans-feruloyl)-beta-D-glucopyranoside (2), 2-(3,4-dihydroxyphenyl)ethyl-O-beta-D-galactopyranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->3)-(6-O-trans-caffeoyl)-beta-D-glucopyranoside (3), 2-(3,4-dihydroxyphenyl)-R,S-methoxy-ethyl-O-beta-D-galactopyranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->3)-(4-O-trans-caffeoyl)-beta-D-glucopyranoside (4) and 2-(3-hydroxy-4-methoxyphenyl)ethyl-O-alpha-L-rhamnopyranosyl-(1-->3)-beta-D-glucopyranosyl-(1-->6)-(4-O-cis-feruloyl)-beta-D-glucopyranoside (5). In addition, the radical-scavenging activities of compounds 1-4 on 1,1-diphenyl-2-picrylhydrazyl radical were examined.