Metal-catalyzed Stereoselective and Protecting-group-free Synthesis of 1,2-cis-Glycosides Using 4,6-Dimethoxy-1,3,5-triazin-2-yl Glycosides as Glycosyl Donors

2015 ◽  
Vol 44 (6) ◽  
pp. 846-848 ◽  
Author(s):  
Tomonari Tanaka ◽  
Naoya Kikuta ◽  
Yoshiharu Kimura ◽  
Shin-ichiro Shoda
Keyword(s):  
Protecting Group ◽  
Metal Catalyzed ◽  
Glycosyl Donors

Mechanistic Study on Gold(I)-Catalyzed Unsaturated Spiroketalization Reaction

2022 ◽  
Vol 19 ◽  
Author(s):  
Kamlesh Sharma
Keyword(s):  
Activation Barrier ◽  
Ring Formation ◽  
Hydroxyl Group ◽  
Mechanistic Study ◽  
Protecting Group ◽  
Wide Range ◽  
Oxocarbenium Ion ◽  
Metal Catalyzed ◽  
Insight Into ◽  
Mechanism Of The Reaction

Abstract: The mechanism of metal-catalyzed spiroketalization of propargyl acetonide is explored by employing DFT with the B3LYP/6-31+G(d) method. Acetonide is used as a regioselective regulator in the formation of monounsaturated spiroketal. The energies of transition states, intermediates, reactants and products are calculated to provide new insight into the mechanism of the reaction. The energetic features, validation of the observed trends in regioselectivity are conferred in terms of electronic indices via FMO analysis. The presence of acetonide facilitates a stepwise spiroketalization as it masks the competing nucleophile, and thus hydroxyl group present, exclusively acts as a nucleophile. The vinyl gold intermediate 3 is formed from 2 via activation barrier TS1. This is the first ring formation, which is 6-exo-dig cyclization. The intermediate 3 is converted into allenyl ether 4, which isomerizes to the intermediate oxocarbenium ion 5 via activation barrier TS2. The intermediate 5 cyclizes to 6 via TS3. This is the second ring formation. The intermediate 6 on protodeauration turns into 6,6-monounsaturated spiroketal 7. It is concluded that acetonide as a protecting group serves the purpose, and thus a wide range of spiroketals can be prepared, regioselectivity.

scholarly journals Protecting group-free, selective cross-coupling of alkyltrifluoroborates with borylated aryl bromides via photoredox/nickel dual catalysis

2015 ◽  
Vol 112 (39) ◽  
pp. 12026-12029 ◽  
Author(s):  
Yohei Yamashita ◽  
John C. Tellis ◽  
Gary A. Molander
Keyword(s):  
Small Molecules ◽  
Functional Group ◽  
Cross Coupling ◽  
Differential Protection ◽  
Coupling Reactions ◽  
Protecting Group ◽  
Cross Coupling Reactions ◽  
Aryl Bromides ◽  
Rapid Construction ◽  
Metal Catalyzed

Orthogonal reactivity modes offer substantial opportunities for rapid construction of complex small molecules. However, most strategies for imparting orthogonality to cross-coupling reactions rely on differential protection of reactive sites, greatly reducing both atom and step economies. Reported here is a strategy for orthogonal cross-coupling wherein a mechanistically distinct activation mode for transmetalation of sp3-hybridized organoboron reagents enables C-C bond formation in the presence of various protected and unprotected sp2-hybridized organoborons. This manifold has the potential for broad application, because orthogonality is inherent to the activation mode itself. The diversification potential of this platform is shown in the rapid elaboration of a trifunctional lynchpin through various transition metal-catalyzed processes without nonproductive deprotection or functional group manipulation steps.

Early transition metal-catalyzed C–H alkylation: hydroaminoalkylation for Csp3–Csp3 bond formation in the synthesis of selectively substituted amines

2018 ◽  
Vol 54 (89) ◽  
pp. 12543-12560 ◽  
Author(s):  
P. M. Edwards ◽  
L. L. Schafer
Keyword(s):  
Transition Metal ◽  
Bond Formation ◽  
Protecting Group ◽  
Early Transition Metal ◽  
Directing Group ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed ◽  
Early Transition

Protecting group, directing group, and external oxidant free synthesis of structurally diverse amines.

Stereoselective Synthesis of Diglycosyl Diacylglycerols with Glycosyl Donors Bearing a β-Stereodirecting 2,3-Naphthalenedimethyl Protecting Group

2020 ◽  
Vol 85 (24) ◽  
pp. 16166-16181
Author(s):  
Nahoko Yagami ◽  
Amol M. Vibhute ◽  
Hide-Nori Tanaka ◽  
Naoko Komura ◽  
Akihiro Imamura ◽  
...  
Keyword(s):  
Stereoselective Synthesis ◽  
Protecting Group ◽  
Glycosyl Donors

New Effective Synthesis of (N-Acetyl- and N-Stearoyl-2-amino-2-deoxy-β-D-glucopyranosyl)-(1→4)-N-acetylnormuramoyl-L-2-aminobutanoyl-D-isoglutamine, Analogs of GMDP with Immunopotentiating Activity

1998 ◽  
Vol 63 (4) ◽  
pp. 577-589 ◽  
Author(s):  
Miroslav Ledvina ◽  
Daniel Zyka ◽  
Jan Ježek ◽  
Tomáš Trnka ◽  
David Šaman
Keyword(s):  
Protecting Group ◽  
Silver Triflate ◽  
Effective Synthesis ◽  
Methyl Triflate ◽  
Glycosyl Donors

Ethyl 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside (5), prepared by benzylation of ethyl 2-deoxy-2-phthalimido-1-thio-β-D-glucopyranoside (4), was transformed by reaction with bromine into 3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide (6). Thioglycoside 5 in the presence of methyl triflate and glycosylbromide 6 in the presence of silver triflate were used as glycosyl donors for condensation with benzyl 2-acetamido-3-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranoside (7), to give benzyl 2-acetamido-3-O-allyl-6-O-benzyl-4-O-(3,4,6-tri-O-benzyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-2-deoxy-α-D-glucopyranoside (8). Its reductive dephthaloylation with NaBH4/AcOH afforded benzyl 2-acetamido-3-O-allyl-4-O-(2-amino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)- 6-O-benzyl-2-deoxy-α-D-glucopyranoside (11). Compound 11 was N-acylated to give benzyl 2-acetamido-4-O-(2-acylamino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)-3-O-allyl-6-O-benzyl-2-deoxy-α-D-glucopyranosides (12a) or (12b). These compounds were converted into corresponding benzyl 2-acetamido-4-O-(2-acylamino-3,4,6-tri-O-benzyl-2-deoxy-β-D-glucopyranosyl)-6-O-benzyl-3-O-carboxymethyl-2-deoxy-α-D-glucopyranosides which, by condensation with H-L-Abu-D-isoGln(OBzl) followed by hydrogenolysis of protective benzyl groups, furnished glycopeptides 16a and 16b. Intramolecular O→N migration of the allyl protecting group followed by its reduction to the propyl residue by reaction of compound 8 with hydrazine or hydrazinium acetate, to give benzyl 2-acetamido-4-O-(3,4,6-tri-O-benzyl-2-deoxy-2-propylamino-β-D-glucopyranosyl)-6-O-benzyl-2-deoxy-α-D-glucopyranoside (9), is also described.

Synthesis of Structurally Simplified Aureolic Acid Aglycone-C-D-E Trisaccharide Analogues

2002 ◽  
Vol 55 (2) ◽  
pp. 113 ◽  
Author(s):  
W. R. Roush ◽  
N. A. Powell ◽  
R. A. James
Keyword(s):  
Dna Binding ◽  
Complex Formation ◽  
Deoxyribonucleic Acid ◽  
Single Step ◽  
Protecting Group ◽  
Acetate Ester ◽  
Aureolic Acid ◽  
Glycosyl Donors

Syntheses of aureolic acid analogues (5) and (6) with (2S)- and (2R)-acyloin stereochemistry, respectively, are described. The synthesis of (5) utilizes a `C + DE' glycosidation sequence, whereas analogue (6), with unnatural (2R)-acyloin stereochemistry, was synthesized by a sequence in which the entire C-D-E trisaccharide was introduced in a single step. While these syntheses provided sufficient quantities of the two aureolic acid analogues for use in studies of Mg2+ complex formation and deoxyribonucleic acid (DNA) binding, this work also highlights certain limitations in the use of 2-thiophenyl glycosyl donors for synthesis of 2-deoxy-β-glycosides. Specifically, difficulties were encountered in the identification of a protecting group for the aglycone C8 phenol that is fully compatible with the conditions required for reductive removal of the thiophenyl substituents after completion of the glycosidation sequence. Sensitivity of the C2 acyloin stereocentre to the conditions required for deprotection of a phenolic acetate ester are also highlighted in the syntheses of (5), and especially of (6).

Protecting Group Dependence of Stereochemical Outcome of Glycosylation of 2-O-(Thiophen-2-yl)methyl Ether Protected Glycosyl Donors

2016 ◽  
Vol 2016 (8) ◽  
pp. 1520-1532 ◽  
Author(s):  
Andrew J. A. Watson ◽  
Stewart R. Alexander ◽  
Daniel J. Cox ◽  
Antony J. Fairbanks
Keyword(s):  
Methyl Ether ◽  
Protecting Group ◽  
Glycosyl Donors

scholarly journals Exploration of C–H and N–H-bond functionalization towards 1-(1,2-diarylindol-3-yl)tetrahydroisoquinolines

2014 ◽  
Vol 10 ◽  
pp. 2186-2199 ◽  
Author(s):  
Michael Ghobrial ◽  
Marko D Mihovilovic ◽  
Michael Schnürch
Keyword(s):  
Transition Metal ◽  
Synthetic Approach ◽  
Protecting Group ◽  
Copper Salts ◽  
Bond Functionalization ◽  
Palladium Catalyzed ◽  
Synthetic Routes ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

The synthesis of 1,2,3-trisubstituted indoles was investigated. More specifically, straightforward synthetic routes towards 1-(1,2-diarylindol-3-yl)-N-PG-THIQs (PG = protecting group, THIQ = tetrahydroisoquinoline) employing transition metal-catalyzed C–H and N–H-bond functionalization were explored. It was found that the synthesis of the target compounds is strongly dependent on the order of events. Hence, depending on the requirements of a synthetic problem the most suitable and promising pathway can be chosen. Additionally, a new synthetic approach towards 1,2-diarylindoles starting from 1-arylindole could be established in the course of our investigation by using a palladium-catalyzed protocol. Such 1,2-diarylindoles were successfully reacted with N-Boc-THIQ to furnish 1,2,3-trisubstituted indoles as target compounds. Furthermore, regioselective N-arylation of protected and unprotected 1-(indol-3-yl)-THIQs was successfully conducted using either simple iron or copper salts as catalysts.

ChemInform Abstract: 2,4-Dimethoxybenzyl: An Amide Protecting Group for 2-Acetamido Glycosyl Donors.

ChemInform ◽  
2010 ◽  
Vol 33 (19) ◽  
pp. no-no
Author(s):  
Nicholas M. Kelly ◽  
Knud J. Jensen
Keyword(s):  
Protecting Group ◽  
Glycosyl Donors
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