- Slow glycosylation: Activation of trichloroacetimidates under mild conditions using lithium salts and the role of counterions
-
Glycosylations were carried out with the two glycosyl donors 4-O-acetyl-2,3-O-isopropylidene-1-O-trichloroacetimidoyl-α-L-rhamnopyranose and 2,3,4-tri-O-benzyl-1-O-trichloro-acetimidoyl-α-L-rhamnopyranose in combination with the two alcohols 1-adamantanol and L-menthol as model glycosyl acceptors. As catalysts, the five lithium salts LiNTf2, LiI, LiClO4, LiPF6 and LiOTf were investigated. We demonstrated that both lithium and the respective counterions are playing a role in the activation of trichloroacetimidate glycosyl donors at rt. Under these very mild conditions, the glycosylations are slow and completed in two to eight days. Depending on the counterion, the rate and yield of the reaction differs; however, the selectivity of all investigated lithium salts is deficient.
- Korber, Nora Katharina,Pedersen, Christian Marcus
-
supporting information
(2022/01/19)
-
- Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B
-
This article describes a concise synthesis of cardiotonic steroids oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via three-step sequences. These studies feature an expedient installation of the β16-oxidation based on β14-hydroxyl-directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to oleandrigenin (7) in 12 steps (LLS) and a 3.1% overall yield from 8. The synthetic oleandrigenin (7) was successfully glycosylated with l-rhamnopyranoside-based donor 28 using a Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in a 66% yield (two steps).
- Fejedelem, Zachary,Carney, Nolan,Nagorny, Pavel
-
p. 10249 - 10262
(2021/07/31)
-
- A concise synthesis of rhamnan oligosaccharides with alternating α-(1→2)/(1→3)-linkages and repeating α-(1→3)-linkages by iterative α-glycosylation using disaccharide building blocks
-
A concise synthetic route to rhamnan oligosaccharides with alternating α-(1→2)/(1→3)-linkages and repeating α-(1→3)-linkages is reported. This synthesis was achieved by iterative α-glycosylation using disaccharide building blocks and through orthogonal co
- Tanaka, Hidenori,Hamaya, Yu,Nishiwaki, Nagatoshi,Ishida, Hideharu
-
-
- Synthesis of all eight stereoisomeric 6-deoxy-l-hexopyranosyl donors - Trends in using stereoselective reductions or mitsunobu epimerizations
-
The synthesis of all eight rare but biologically important 6deoxy-L-hexoses as their thioglycoside glycosyl donors starting from the commercially available L-rhamnose or L-fucose is reported. The synthesis of all eight 6-deoxy-L-hexoses was accomplished u
- Frihed, Tobias Gylling,Pedersen, Christian Marcus,Bols, Mikael
-
p. 7924 - 7939
(2015/02/18)
-
- Using biological performance similarity to inform disaccharide library design
-
Designing better small-molecule discovery libraries requires having methods to assess the consequences of different synthesis decisions on the biological performance of resulting library members. Since we are particularly interested in how stereochemistry
- Tanikawa, Tetsuya,Fridman, Micha,Zhu, Wenjiang,Faulk, Brian,Joseph, Isaac C.,et al.
-
supporting information; experimental part
p. 5075 - 5083
(2009/09/30)
-
- Facile oxidative cleavage of 4-O-benzyl ethers with dichlorodicyanoquinone in rhamno- and mannopyranosides
-
On exposure to dichlorodicyanoquinone in wet dichloromethane at room temperature, equatorial 4-O-benzyl ethers are removed with moderate selectivity in the presence of other benzyl ethers in glycopyranosides and glycothiopyranosides.
- Crich, David,Vinogradova, Olga
-
p. 3581 - 3584
(2008/02/04)
-
- Glycodiversification for the optimization of the kanamycin class aminoglycosides
-
In an effort to optimize the antibacterial activity of kanamycin class aminoglycoside antibiotics, we have accomplished the synthesis and antibacterial assay of new kanamycin B analogues. A rationale-based glycodiversification strategy was employed. The a
- Wang, Jinhua,Li, Jie,Chen, Hsiao-Nung,Chang, Huiwen,Tanifum, Christabel Tomla,Liu, Hsiu-Hsiang,Czyryca, Przemyslaw G.,Chang, Cheng-Wei Tom
-
p. 6271 - 6285
(2007/10/03)
-
- Conformational analysis of sulfur-containing 6-deoxy-L-hexose derivatives by molecular modeling and NMR spectroscopy. A theoretical study and experimental evidence of intramolecular nonbonded interactions between sulfur and oxygen
-
6-Deoxy-L-mannose diphenyldithioacetal (1) unexpectedly gave the rearranged products phenyl 3,4-di-O-acetyl-2-S-phenyl-1,2-dithio-6-deoxy-β -L-glucopyranoside (9) and 3,4-di-O-acetyl-2,5-anhydro-6-deoxy-L-glucose diphenyldithioacetal (10) upon treatment w
- Fragoso-Serrano, Mabel,Guillen-Jaramillo, Georgina,Pereda-Miranda, Rogelio,Cerda-Garcia-Rojas, Carlos M.
-
p. 7167 - 7175
(2007/10/03)
-
- RSK INHIBITORS AND THERAPEUTIC USES THEREOF
-
The present invention is directed to novel compounds and compositions that have Rsk specific inhibitory activity. In addition, inhibition of Rsk by the present compounds has been discovered to halt the proliferation of cancer cell lines while having little effect on the proliferation rate of normal cells. Therefore, the present invention identifies Rsk as a target for therapeutic intervention in diseased states in which the disease or the symptoms can be ameliorated by inhibition of Rsk catalytic activity.
- -
-
-
- Total synthesis of calonyctin A2, a macrolidic glycolipid with plant growth-promoting activity
-
Calonyctin A2, a tetrasaccharidic glycolipid having a 22-membered macrolidic structure, has been synthesized by the assembly of three 6- deoxygenated thioglycoside intermediates. The short-step synthesis was achieved by preparation of the most complicated
- Furukawa, Jun-Ichi,Kobayashi, Shigeru,Nomizu, Motoyoshi,Nishi, Norio,Sakairi, Nobuo
-
p. 3453 - 3457
(2007/10/03)
-
- β-Acarbose. VIII the synthesis of some N-linked carba-oligosacchandes
-
Two carbohydrate triflates have been used to alkylate a 1-epivalienamine derivative to give small amounts of the desired secondary amines, in addition to amounts of the products of elimination. Deprotection of the secondary amines afforded a carba-disacch
- Stick, Robert V.,Tilbrook, D. Matthew G.,Williams, Spencer J.
-
p. 895 - 904
(2007/10/03)
-
- Enzymatic esterification and de-esterification of carbohydrates: synthesis of a naturally occurring rhamnopyranoside of p-hydroxybenzaldehyde and a systematic investigation of lipase-catalysed acylation of selected arylpyranosides
-
The regiocontrolled esterification and de-esterification of mono- and di-saccharides is reviewed.New results involving the enzyme-catalysed regioselective acylation of ribo-110, arabino-112, 119, xylo-111, and rhamnopyranosides 116, 118 (as well as two ar
- Bashir, Nazir B.,Phythian, Sara J.,Reason, Andrew J.,Roberts, Stanley M.
-
p. 2203 - 2222
(2007/10/02)
-
- Total synthesis of calicheamicin γ1I. 1. Synthesis of the oligosaccharide fragment
-
The first total synthesis of the calicheamicin γ1I oligosaccharide fragment in the form of its methyl glycoside (62) has been achieved. The synthetic challenge of the B-ring was recognized and studied initially, resulting in a novel and unique solution to the stereochemical problems posed involving a [3,3]-sigmatropic rearrangement of an allylic thionoimidazolide (111). This chemistry was initially worked out on a model for the ABC-ring system (47) and then successfully applied to the real system. The success of this synthesis has enabled the completion of the first synthesis of the natural product itself, calicheamicin γ1I (1), as will be described in the following papers in this issue.
- Groneberg,Miyazaki,Stylianides,Schulze,Stahl,Schreiner,Suzuki,Iwabuchi,Smith,Nicolaou
-
p. 7593 - 7611
(2007/10/02)
-
- A simple method for avoiding alkylthio group migration during the synthesis of thioglycoside 2,3-orthoesters. An improved synthesis of partially acylated 1-thio-α-L-rhamnopyranosides
-
A fast, technically simple and high-yielding procedure is described for the preparation of the 2,3-cyclic orthoesters of methyl, ethyl, and phenyl 1-thio-α-L-rhamnopyranosides. The method prevents alkylthio group migration during the synthesis of thioglycoside 2,3-orthoesters. Considering the high yields, short reaction times and operational simplicity, this method is a substantial improvement over the procedures previously proposed for the synthesis of partially acylated 1-thio-α-L-rhamnopyranosides.
- Pozsgay
-
p. 295 - 302
(2007/10/02)
-
- Building Units of Oligosaccharides, CIII. - Synthesis of Modified Derivatives of the Disaccharide β-D-Gal-(1->3)-α-D-GalNAc for the Examination of Substrate Specifities of Core 2-β6-GlcNAc-Transferase and α-3-Sialyltransferase Involved in the Biosynthesis
-
Derivatives of benzyl β-D-galactopyranosyl-(1->3)-2-acetamido-2-deoxy-α-D-galactopyranoside have been synthesized.The 6'-, 4'- and 3'-OH group of the galactose moiety as well as the 6- and 4-OH and the 2-acetamido group of the 2-acetamido-2-deoxy-D-galact
- Paulsen, Hans,Rutz, Volker,Brockhausen, Inka
-
p. 747 - 758
(2007/10/02)
-