Left-Handed Helix of Three-Membered Ring Amino Acid Homopeptide Interrupted by an N–H···Ethereal O-Type Hydrogen Bond

2018 ◽  
Vol 20 (24) ◽  
pp. 7830-7834 ◽  
Author(s):  
Yurie Koba ◽  
Atsushi Ueda ◽  
Makoto Oba ◽  
Mitsunobu Doi ◽  
Takuma Kato ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Amino Acid ◽  
Membered Ring ◽  
Left Handed ◽  
Type Hydrogen Bond

Long-range ?-type hydrogen bond in dimers CH2?HF, CH2O?H2O, and CH2O?NH3

2005 ◽  
Vol 103 (2) ◽  
pp. 157-166 ◽  
Author(s):  
Rui Yan Li ◽  
Zhi Ru Li ◽  
Di Wu ◽  
Xi Yun Hao ◽  
Ru Jiao Li ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Long Range ◽  
Range Type ◽  
Type Hydrogen Bond

scholarly journals 14,15-Didehydrohellebrigenin

2012 ◽  
Vol 68 (6) ◽  
pp. o1614-o1615
Author(s):  
Tong Yu ◽  
Hai-Yan Tian ◽  
Xiao-Feng Yuan ◽  
Shu-Zhi Hu ◽  
Ren-Wang Jiang
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Lactone Ring ◽  
Three Dimensional ◽  
Membered Ring ◽  
Envelope Conformation ◽  
Compound C ◽  
Dimensional Network ◽  
Hydroxy Groups

The title compound, C24H30O5, is the didehydro product of the steroid hellebrigenin (systematic name: 3β,5,14-trihydroxy-19-oxo-5β-bufa-20,22-dienolide). It consists of three cyclohexane rings (A, B and C), a five-membered ring (D) and a six-membered lactone ring (E). The stereochemistry of the ring junctions are A/B cis, B/C trans and C/D cis. Cyclohexane rings A, B and C have normal chair conformations. The five-membered ring D with the C=C bond adopts an envelope conformation. Lactone ring E is essentially planar with a mean derivation of 0.006 (4) Å and is β-oriented at the C atom of ring D to which it is attached. There is an O—H...O hydrogen bond in the molecule involving the hydroxy groups. In the crystal, O—H...O hydrogen bonds link the molecules into chains propagating along [010]. The chains are linked by C—H...O contacts into a three-dimensional network.

scholarly journals Комбинационное рассеяние света в хирально чистых и рацемической фазах поликристаллов триптофана и тирозина

2019 ◽  
Vol 127 (10) ◽  
pp. 541
Author(s):  
В.С. Горелик ◽  
М.Ф. Умаров ◽  
Ю.П. Войнов
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Raman Spectra ◽  
Spectral Range ◽  
Phase State ◽  
Source Parameters ◽  
Low Frequency ◽  
Aromatic Amino Acids ◽  
Chiral Phase ◽  
Left Handed

AbstractRaman spectra of tryptophan and tyrosine polycrystals have been analyzed in a wide spectral range by fiber-optic spectroscopy. The Raman spectra have been recorded with a BWS465-785H spectrometer in the spectral range of 0–2700 cm^–1 using a 785-nm cw laser as an excitation source. Parameters of the Raman spectra are compared for three crystalline phase modifications of aromatic amino acids: left-handed, right-handed, and racemic phase. The presence of strong Raman satellites, the characteristics of which change depending on the type of the chiral phase state of amino acid, is found in the low-frequency Raman spectra of tryptophan and tyrosine amino acid lattices. The results obtained can be used for monitoring the chiral purity of bioactive preparations containing amino acids.

scholarly journals 2-Oxo-2H-chromen-7-yl 4-methylbenzoate

IUCrData ◽  
2018 ◽  
Vol 3 (7) ◽  
Author(s):  
Abdoulaye Djandé ◽  
Akoun Abou ◽  
Félix Kini ◽  
Konan René Kambo ◽  
Michel Giorgi
Keyword(s):  
Hydrogen Bond ◽  
Title Compound ◽  
Acute Angle ◽  
Membered Ring ◽  
Hirshfeld Surface ◽  
Supramolecular Interactions ◽  
Stacking Interactions ◽  
Weak Hydrogen Bond ◽  
Compound C ◽  
Benzene Rings

In the title compound, C17H12O4, the benzoate ring is oriented at an acute angle of 60.14 (13)° relative to the coumarin plane (r.m.s. deviation = 0.006 Å). This conformation is stabilized by an intramolecular C—H...O weak hydrogen bond, which forms a five-membered ring. Also present are π–π stacking interactions between neighbouring pyrone and benzene rings [centroid-to-centroid distances in the range 3.6286 (1)–3.6459 (1) Å] and C=O...π interactions [O...centroid distances in the range 3.2938 (1)–3.6132 (1) Å]. Hirshfeld surface analysis has been used to confirm and quantify the supramolecular interactions.

scholarly journals Chemistry of Homocysteine Thiolactone in A Prebiotic Perspective

Life ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 40 ◽  
Author(s):  
Ibrahim Shalayel ◽  
Yannick Vallée
Keyword(s):  
Amino Acid ◽  
Membered Ring ◽  
Disulfide Bridges ◽  
Homocysteine Thiolactone ◽  
Metallic Cations ◽  
Neutral Water ◽  
Sulfur Containing

Homocysteine is a non-proteinogenic sulfur-containing amino acid. Like cysteine, it can form disulfide bridges and complex metallic cations. It is also closely related to methionine, the first amino acid in the synthesis of all contemporary proteins. Furthermore, its cyclized form, a five-membered ring thiolactone, is stable in acidic and neutral water. Here, we demonstrate that this thiolactone may have been formed in the primitive ocean directly from the Strecker precursor of homocysteine, an aminonitrile. Even though it is poorly reactive, this thiolactone may be open by some amines, yielding amides which, in turn, could be the precursors of longer peptides.

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