Chiral Acylnitroso Research Articles

ChemInform Abstract: Diastereoselective [4 + 2]Cycloadditions of Acyl Nitroso Compounds.

Abstract A highly diastereoselective route to unsaturated amino alcohol derivatives has been developed that features the [4+2] cycloaddition of chiral acyl nitroso compounds to a variety of conjugated dienes; a useful oxidative method for generating acyl nitroso compounds from the corresponding hydroxamic acids under very mild conditions was also discovered.

ChemInform Abstract: Single and Double Asymmetric Induction in Diels-Alder Cycloadditions with Chiral Acylnitroso Dienophiles.

Abstract Diels-Alder reaction of the achiral 1-silyloxybutadiene 1a with the chiral acyinitroso dienophile 2a gave cycloadduct 4 in high diastereomeric excess (d.e. > 98 %), a result which is undoubtedly due to the C-2 symmetrical chiral dimethylpyrrolidine inductor. Excellent d.e. was also observed when the (R)-prolinol dienophile 2d was reacted with the chiral diene 1b (d.e. = 96 %), whereas cycloaddition of the (S) enantiomer 2e with 1b gave only poor asymmetric induction (d.e. = 4 %). These two latter examples nicely illustrate the influence of “matched pair” (1b/2d) versus “mismatched pair” (1b/2e) upon double asymmetric induction. All herein reported Diels-Alder cycloadditions were regiospecific.

ChemInform Abstract: Enhanced Stereoselectivity in Aqueous Intramolecular Hetero Diels- Alder Cycloaddition of Chiral Acylnitroso Compounds.

Abstract In an aqueous medium, intramolecular hetero Diels-Alder cycloadditions of the chiral acylnitroso compounds, generated from the chiral hydroxamic acids by in situ periodate oxidation, shows a pronounced enhancement of the trans selectivity compared with the results obtained by employing nonaqueous conditions.

ChemInform Abstract: Stereoselective Cycloadditions of Chiral Acyl-Nitroso Compounds. Unexpected Formation of an Oxazolidinone.

Abstract On treatment with either N -phenyltrifluoromethanesulphonimide or p -toluenesulphonyl chloride and base, hydroxamic acid 3 provides the oxazolidinone 4 in moderate yield, probably by a pathway involving fragmentation; Boc derivative 8 is suitable substrate for Pd o catalyzed nucleophilic displacement.

ChemInform Abstract: Development and Applications of Amino Acid‐Derived Chiral Acylnitroso Hetero Diels—Alder Reactions

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of novel hydantoin analogs of 5′-nor carbocyclic nucleosides: Versatility of a chiral acylnitroso cycloaddition

An asymmetric hetero-Diels-Alder reaction involving an amino acid-derived acylnitroso dienophile was utilized to synthesize novel hydantoin analogs ( 12) of carbocyclic nucleosides. The hydantoins were formed during an attempted protection of an amide nitrogen.

ChemInform Abstract: Amino Acid Derived Chiral Acyl Nitroso Compounds: Diastereoselectivity in Intermolecular Hetero Diels‐Alder Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Total synthesis of (−)-pumiliotoxin C by aqueous intramolecular acylnitroso Diels-Alder approach

A chiral approach to (−)-pumiliotoxin C via a stereoselective intramolecular hetero Diels-Alder reaction of a chiral acylnitroso compound performed in an aqueous medium is described.

Amino Acid-Derived Chiral Acyl Nitroso Compounds: Diastereoselectivity in Intermolecular Hetero Diels-Alder Reactions

The diastereoselectivities of chiral acyl nitroso dienophiles derived from optically pure N-protected α-amino hydroxamic acids have been de- termined in intermolecular hetero Diels-Alder reactions. The cycloaddi- tion reactions afforded synthetically useful quantities of functionally rich, optically pure cycloadducts, useful for the preparation of a vari- ety of compounds of potential biological interest. Molybdenum hexacar- bonyl reduction of the cycloadducts gave optically pure allylic alco- hols. Osmium tetraoxide-catalyzed dihydroxylation of several bis-ally- lically substituted intermediates gave only the diastereomerically pure diols corresponding to naturally occurring 2',3'-dihydroxynucleoside analogs

Enhanced stereoselectivity in aqueous intramolecular hetero Diels-Alder cycloaddition of chiral acylnitroso compounds

In an aqueous medium, intramolecular hetero Diels-Alder cycloadditions of the chiral acylnitroso compounds, generated from the chiral hydroxamic acids by in situ periodate oxidation, shows a pronounced enhancement of the trans selectivity compared with the results obtained by employing nonaqueous conditions.

Asymmetric induction in the Diels–Alder reactions of α-hydroxy acyl nitroso compounds

The hydroxamic acids 7, derived from a series of α-hydroxy acids 5, have been oxidised with periodate to form transient, chiral acyl nitroso compounds 8, which were trapped in situ with cyclopentadiene and cyclohex-1,3-diene to give mixtures of diastereoisomeric, Diels–Alder cycloadducts 9 and 10, respectively. Cycloaddition at 0 °C occurred with moderate stereoselectivity, e.g. both the mandeloyl nitroso compound 8a with cyclopentadiene and the tert-butylglycoloyl nitroso compound 8d with cyclohexadiene gave ca. 5:1 mixtures of diastereoisomers. Much higher diastereoselectivities (cycloadduct ratios ca. 10:1 for 9a, 9d and 10d) were observed at –78 °C. The mandeloyl nitroso compound 8a, which can form an intramolecular hydrogen bond between the hydroxy and nitroso groups, showed higher stereoselectivities than its O-methyl ether 8b. The major cycloadduct 13a of the (S)-mandeloyl nitroso compound 12 and cyclohexadiene was degraded to the bicyclic oxazine 15 of known absolute configuration. Formation of the cycloadduct 13a as the major product is consistent with preferential endo addition of the hydrogen bonded nitroso compound 12 from the face anti to the phenyl group.

Diastereoselective [4+2] Cycloadditions of Acyl Nitroso Compounds

A highly diastereoselective route to unsaturated amino alcohol derivatives has been developed that features the [4+2] cycloaddition of chiral acyl nitroso compounds to a variety of conjugated dienes; a useful oxidative method for generating acyl nitroso compounds from the corresponding hydroxamic acids under very mild conditions was also discovered.

Single and double asymmetric induction in Diels-Alder cycloadditions with chiral acylnitroso dienophiles

Diels-Alder reaction of the achiral 1-silyloxybutadiene 1a with the chiral acyinitroso dienophile 2a gave cycloadduct 4 in high diastereomeric excess ( d.e. > 98 %), a result which is undoubtedly due to the C-2 symmetrical chiral dimethylpyrrolidine inductor. Excellent d.e. was also observed when the (R)-prolinol dienophile 2d was reacted with the chiral diene 1b ( d.e. = 96 %), whereas cycloaddition of the (S) enantiomer 2e with 1b gave only poor asymmetric induction ( d.e. = 4 %). These two latter examples nicely illustrate the influence of “matched pair” ( 1b/2d) versus “mismatched pair” ( 1b/2e) upon double asymmetric induction. All herein reported Diels-Alder cycloadditions were regiospecific.

ChemInform Abstract: Stereoselective Cycloadditions of Chiral Acylnitroso Compounds. Synthetically Useful Reactions of the Adducts.

AbstractThe chiral hydroxamic acid (I) is dehydrogenated to generate the acyl nitroso intermediate (II) which undergoes cycloaddition reaction with the cyclic dienes (III), producing the bridged 1,2‐oxazines (IV).

ChemInform Abstract: Stereoselective Cycloadditions of Chiral Acylnitroso Compounds. An Approach to Carbapenem Synthesis.

AbstractThe adduct (I), obtained from a benzoyl nitroso intermediate and cyclopentadiene, is cleaved by aluminum amalgam and then oxidized to give the amidocyclopentenone (II).

ChemInform Abstract: Stereoselective Cycloadditions of Chiral Acylnitroso Compounds.

AbstractOxidation of the hydroxamic acids (I) and (V) in the presence of the cyclic 1,3‐dienes (II) and (VIII) results in cycloaddition reaction, producing predominantly the bicyclic 1,2‐oxazines (III), (VI), and (IX) respectively.

Stereoselective Cycloadditions of Chiral Acyl-Nitroso Compounds

Stereoselective Cycloadditions of Chiral Acyl-Nitroso Compounds

Stereoselective Cycloadditions of Chiral Acyl-Nitroso Compounds

Stereoselective Cycloadditions of Chiral Acyl-Nitroso Compounds