Chiral Aldehydes Research Articles

3 + 2]-Annulation Reactions of Chiral Allylsilanes and Chiral Aldehydes. Studies on the Synthesis of Bis-tetrahydrofuran Substructures of Annonaceous Acetogenins

[Structure: See text] Double asymmetric [3 + 2]-annulation reactions of chiral beta-silyloxyallylsilanes with chiral 2-tetrahydrofuranyl carboxaldehydes have been studied, leading to the stereocontrolled synthesis of six diastereomeric bis-tetrahydrofuran structures corresponding to the core subunits of members of the Annonaceous acetogenin family of natural products. Transition-state models are proposed to account for the stereoselectivity of the double-stereodifferentiating [3 + 2]-annulation reactions.

Reagent controlled addition of chiral sulfur ylides to chiral aldehydes

The degree of reagent and substrate control in the reaction of chiral sulfur ylides with chiral aldehydes has been investigated. Specifically, the reactions of the two enantiomers of the chiral benzyl sulfonium salt 1 with glyceraldehyde acetonide were studied in detail. Of the two new stereogenic centers created, it was found that the C1 stereochemistry was largely controlled by the reagent, whereas control at the C2 center was dependent on the aldehyde used. In one case, the trans isomer was produced via reversible formation of the intermediate betaine, whereas in the alternative case, the C2 center was under Felkin Anh/Cornforth control through non-reversible formation of the betaine. Thus, the aldehyde stereocenter influenced the degree of reversibility in betaine formation, which impacted on the stereocontrol at the C2 position.

Additions of Allyl, Allenyl, and Propargylstannanes to Aldehydes and Imines

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantioselective Recognition of 1,2-Amino Alcohols by Reversible Formation of Imines with Resonance-Assisted Hydrogen Bonds

A chiral aldehyde with three H-bond donating groups (2) has been synthesized. This aldehyde binds a variety of chiral 1,2-amino alcohols in benzene with the same sense of stereoselectivity. Computational and experimental data indicate that one imine bond, one resonance-assisted H-bond to the imine nitrogen, and two H-bonds to the alcoholic oxygen all play an important role in the stereoselective recognition. [structure: see text]

Asymmetric Synthesis of trans-3,4-Dialkyl-γ-butyrolactones via an Acyl-Claisen and Iodolactonization Route

[reaction: see text] A new, efficient, and general asymmetric synthesis of enantiomerically pure trans-3,4-dialkyl-gamma-lactones has been developed. The key steps are (1) copper-catalyzed three-component coupling of chiral amine, aldehyde, and alkyne, (2) acyl-Claisen rearrangement, and (3) iodolactonization. The products, chiral gamma-lactones, are versatile synthetic intermediates and structural units of natural products and modified nucleosides.

Asymmetric Construction of Quaternary Carbon Stereocenters: High Stereoselection in Mukaiyama Aldol Reactions of 2-Siloxyindoles with Chiral Aldehydes

[reaction: see text] A new synthesis of enantiopure 3,3-disubstituted oxindoles by stereoselective Mukaiyama aldol reaction of 3-substituted 2-siloxyindoles and chiral, enantiopure aldehydes having nitrogen or oxygen substituents at the alpha carbon is described. When the C3 substituent of the prochiral nucleophile is aryl or heteroaryl, stereoselectivity is high (10-80:1).

“Double Asymmetric Induction” as a Novel Tool for High Stereocontrol in Baylis—Hillman Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Double Stereodifferentiating Aldol Reactions Based on Chiral Ketones Derived from Lactic Acid: Synthesis of C1—C6 Fragment of Erythronolides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Stereoselective Synthesis of the C9—C19 Lactone‐Dipropionate Fragment of Calyculin C.

A highly diastereoselective synthesis of the title fragment of calyculin C has been developed based on an internal asymmetric induction between a chiral aldehyde and Z-crotyl trifluorosilane.

Synthesis of (4R,5S)-Melithiazols B and M

A Wittig reaction between the reported (+)-chiral aldehyde [(4R,5R)-5] and the phosphoranylide derived from the bithiazole-type phosphonium iodide (6) using lithium bis(trimethylsilyl)amide afforded the (+)-melithiazol B (1), whose spectral data were identical with those of the natural (+)-1 from the myxobacterium Archangium gephyra, strain Ar 7747. Moreover, the selective olefin formation between (+)-(4R,5R)-5 and the bithiazole-type sulfone [(′)-7] followed by transformation gave the (+)-melithiazol M (2), whose spectral data were identical with those of the natural (+)-2 from the myxobacterium Archangium gephyra, strain Ar 7747.

Stereoselective synthesis of (E)-trisubstituted α,β-unsaturated amides and acids

Potassium alkoxides of N-acyl-oxazolidin-2-one-syn-aldols undergo stereoselective elimination reactions to afford a range of trisubstituted (E)-alpha,beta-unsaturated amides in >95% de, that may be subsequently converted into their corresponding (E)-alpha,beta-unsaturated acids or (E)-alpha,beta-unsaturated oxazolines in good yield. syn-Aldols derived from alpha,beta-unsaturated aldehydes gave their corresponding trisubstituted (E)-alpha,beta-unsaturated-amides with poorer levels of diastereocontrol, whilst there was a similar loss in (E)-selectivity during elimination of syn-aldols derived from chiral aldehydes. These elimination reactions proceed via rearrangement of the potassium alkoxide of the syn-aldol to a 1,3-oxazinane-2,4-dione enolate intermediate that subsequently eliminates carbon dioxide to afford a trisubstituted (E)-alpha,beta-unsaturated amide. The (E)-selectivity observed during the E1cB-type elimination step has been rationalised using a simple conformational model that employs a chair-like transition state to explain the observed stereocontrol.

Highly Stereoselective Addition of Silylphosphines to Chiral Aldehydes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Formal Total Synthesis of Oximidine II via a Suzuki‐Type Cross‐Coupling Macrocyclization Employing Potassium Organotrifluoroborates.

A formal total synthesis of oximidine II has been achieved, employing a Suzuki-type coupling approach to construct the highly strained, polyunsaturated 12-membered macrolactone. To achieve this goal, benefit was derived from the stability of potassium alkenyltrifluoroborates to establish conditions for the macrocyclization. The stereocontrolled formation of the cis-1,2-diol subunit was accomplished using a diastereoselective, reagent controlled addition to a chiral aldehyde utilizing the Carreira protocol. Advantage was taken of the Snieckus hydroborating reagent to gain access to the key trifluoroborate needed for the macrocyclization.

Desymmetrizing Hydroformylation with the Aid of a Planar Chiral Catalyst‐Directing Group.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Addition of lactate-derived chiral allyltrichlorostannanes to chiral aldehydes

Chiral lactate-derived allyltrichlorostannanes reacted with chiral α-methyl β-alkoxy and syn and anti α-methyl-β-alkoxy aldehydes to give the corresponding homoallylic alcohols with moderate to high 1,4- syn-diastereoselectivities.

Highly stereoselective addition of diphenyl(trimethylsilyl)phosphine to a chiral aldehyde

Highly stereoselective addition of diphenyl(trimethylsilyl)phosphine to a chiral aldehyde

Stereoselective synthesis of the C 9–C 19 lactone-dipropionate fragment of calyculin C

A highly diastereoselective synthesis of the title fragment of calyculin C has been developed based on an internal asymmetric induction between a chiral aldehyde and Z-crotyl trifluorosilane.

Truncated Diastereoselective Passerini Reaction, a Rapid Construction of Polysubstituted Oxazole and Peptides Having an α‐Hydroxy‐β‐amino Acid Component.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly stereoselective addition of silylphosphines to chiral aldehydes

The reaction between diphenyl(trimethylsilyl)phosphine and chiral aldehydes proceeds with high stereoselectivity to give diastereomerically pure tertiary α-trimethylsiloxyalkylphosphines. The diastereomeric purity of the addition products was 90–100%. The products were purified via the formation of borane–phosphine complexes. The reaction of bis(trimethylsilyl)phenylphosphine with acetonide ( R)-glyceraldehyde provides tertiary bis(glyceryl)phosphines.

Desymmetrizing hydroformylation with the aid of a planar chiral catalyst-directing group.

Desymmetrizing hydroformylation of bisalkenyl- and bisallylcarbinols could be achieved employing a chiral substrate-bound catalyst-directing group (o-DPPF) with excellent levels of diastereotopic alkene face and diastereotopic alkene group discrimination to give bifunctionalized chiral aldehydes in enantiomerically pure form.