An efficient and highly diastereoselective synthesis of C-glycosylated 1,3-oxazolidines from N-methyl-D-glucamine (original) (raw)
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Chiral N -Acyloxazolidines: Synthesis, Structure, and Mechanistic Insights †
The Journal of Organic Chemistry, 2008
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Organocatalytic Asymmetric Synthesis of 2,5‐Disubstituted Oxazolidines
Advanced Synthesis & Catalysis, 2018
The first organocatalytic asymmetric synthesis of 2,5-disubstituted oxazolidines has been developed via hemiaminal formation between alkyl aldehydes and N-tosyl aminomethyl enones followed by intramolecular oxa-Michael reaction. Quinine derived bifunctional squaramide catalyst was found to be efficient for this reaction and a variety of alkyl aldehydes and N-tosyl aminomethyl enones were employed.
Tetrahedron, 1994
An improved synthesis of 2-(T-pyridyl)-2-aminoalcohols la and lb, in enantiomerically pore form via 1,3-oxazolidine derivatives is presented. Some efficient and selective methods for both the cleavage of the oxazolidine ring and the removal of the N-Boc px%ecting group are also mported. Optically active amiuo alcohols are of relevance as tools in asymmetric processes.2J~4 Very recently we have reported the preparation of (R)-2-amino-2-(2'-pyridyl)ethan-l-01 (la) and (lR,2R)-l-amino-l-Q'pyridyl)propan-2-01 (lb) starting from natural L-serine and L-threonine by means of a multistep reaction sequence, in ca. 25 % overall yield.1 H2 H2 la lb In the context of a project designed to use these compounds in asymmetric reactions, such as the alkylation of aldehydes with dialkylzinc reagents.3 the reduction of ketones to alcohols with boranes4 and for the preparation of bis ox-line derivatives with C2 axial symmetry? we required au efficient route to prepare multigram quantities of both la and lb. In this paper we wish to describe a very simple preparation of N-tbutoxycarbonyl-or N-benzoyl-protected 4-(2'~pyridyl)-1,3-oxazolidines 5a-c as versatile precursors of la and lb. Efficient procedures for the selective removal of the N-protecting groups are also reported. Compounds lab were achieved through a five step reaction sequence (Scheme 1) with 60% overall yield without loss of enantiomeric excess. Q-N-Benzoyl-1.3-oxazolidine-4-carboxylic acid (2b) was obtained as previously described for the D enantiomer.6 Through a simple modification, (S)-N-t-butoxycarbonyl-1,3-oxazolidine4carboxylic acid (20) and (4S,5R)-N-t-butoxyc~~nyl-5-~~yl-1,3-oxazolidine-4-c~xylic acid (2~) were obtained by reaction of L-serine or L-threonine with formaldehyde (aq 37%. NaOH 2N), followed by trapping with Boc20 up to 250 mm01 scale, in a facile one pot reaction (Scheme 1).
Tetrahedron: Asymmetry, 1996
N-Arylsulfonamides of (R)-and (S)-2-anfmo-l-butanol, on condensation with aromatic aldehydes produced diastereomerically pure 2-aryl-3-arenesulfonyl 4-ethyl-l,3oxazolidines. The absolute configurations of one enantiomeric pair have been determined from two fully refined X-ray structures, supplemented by nmr data.Copyrighi © 1996 Elsevier Science Ltd 3-(p-Toluene sulfonyl)-l,3-oxazolidines derived from enantiomerically pure 13-amino alcohols have been recognized as valuable chiral templates in asymmetric synthesis t. Previous investigations into the condensation of aldehydes with 13-aminoalcohols have shown that the products obtained were found to be an equilibrium mixture of imines and the corresponding 1,3-oxazolidines ~3. Here we wish to report the (R)
Novel Stereoselective Synthesis of Functionalized Oxazolidinones from Chiral Aziridines
The Journal of Organic Chemistry, 2003
Enantiomerically pure N-(R)-R-methylbenzyl-4(R)-(chloromethyl)oxazolidinones (4R)-5a-k were synthesized in one step and high yields from various aziridine-2-methanols (S)-2a-k by intramolecular cyclization with phosgene. The R-methylbenzyl substituent on the nitrogen was easily cleaved to give both enanatiomers of 4-(chloromethyl)oxazolidinones (R)-7a and (S)-7a. (R)-7a was used for the efficient syntheses of (L)-homophenylalaninol analogues (S)-12a-j. We also applied the same methodology to prepare oxazolidinones 9a-c containing a heteroatom-substituted alkyl group at C-4 in high yields.
Frontiers in Chemistry
A new synthetic route to N-alkyl-2-acylazetidines was developed through a highly stereoselective addition of organolithiums to N-alkyl-2-oxazolinylazetidines followed by acidic hydrolysis of the resulting oxazolidine intermediates. This study revealed an unusual reactivity of the C=N bond of the oxazoline group when reacted with organolithiums in a non-polar solvent such as toluene. The observed reactivity has been explained considering the role of the nitrogen lone pair of the azetidine ring as well as of the oxazolinyl group in promoting a complexation of the organolithium, thus ending up with the addition to the C=N double bond. The high level of stereoselectivity in this addition is supported by DFT calculations and NMR investigations, and a model is proposed for the formation of the oxazolidine intermediates, that have been isolated and fully characterized. Upon acidic conditions, the oxazolidine moieties were readily converted into 2-acylazetidines. This synthetic approach has been applied for the preparation of highly enantioenriched 2-acylazetidines starting from chiral not racemic Nalkyl-2-oxazolinylazetidines.
The Journal of Organic Chemistry, 1993
Oxazolidine-24himeg 2-thioxotelrahydr~ 13-oxazines; sugar isothiocyanates: cyclic thiocarbamates; carbohydrates as chill templates Abstmct~ Triethylamine-induced cyclization of methyl 6-desoxy&isothiocyanato-a-Dglucopyranoside (2) yields the fused 2-thioxotetrahydro-1.3-oxazine derivative 4. In contrast, bdeoxy-1,2:3.4-di-0-isopropyliden-6-isothiocyanato-aD -galactopyranose (5) undergoes, on deprotection, spontaneous cyclization involving the OH-5 of the galactofumnose tautomer to give the oxazolidine-2tbione derivative 7. The chirality of the resulting substituted heterocycles is determined by the sugar configuration. 1,3-Oxazolidine-2-thiones (1, n = 2) are of interest because some of the naturally occurring members1 show antithyroid activity. The six-membered analogues tetrahydro-1,3-oxazine-2-thiones (1, n = 3) have shown antidepressant, anticholinergic, analgesic, and antiinflammatory activityz.