Asymmetric Synthesis of Highly Substituted γ-Amino Acids from Allyltitanium Sulfoximines

Abstract

[structure: see text]. Asymmetric syntheses of the highly substituted protected gamma-amino acids 10a, 10b, 18, and 21 have been developed starting from the allyltitanium sulfoximines V and VI, respectively, and furan-2-carbaldehyde.

Sulfoximine‐Based Modular Enantioselective Synthesis of Azaspirocycles Featuring Sulfoximine Displacement, Dianion Cycloalkylation, RCM and N‐Acyliminium Ion Formation

“…Stereoselective generation of the C–N bond of Ia – c was accomplished by the carbamate method,9 which we have successfully used for the stereoselective amination of mainly acyclic δ‐hydroxy alkenylsulfoximines (see below) 6c,10. Thus, treatment of alcohols 3 and 4 with trichloroacetyl isocyanate and subsequent hydrolysis of the corresponding N ‐trichloroacetyl carbamates with ammonium carbonate in methanol furnished the corresponding crude carbamates 5 and 6 , respectively.…”

“…6c Presumably, formation of N–H ·· N bonds in 7 and 11 is unfavourable because of destabilising steric interactions between the phenyl group and either the carbocycle or the methyl group. We had already prepared, in the context of the synthesis of γ‐hydroxy β‐amino acids, bicyclic oxazinanones 9 and 10 , each with 98 % de or higher, by the carbamate method 10. Oxazinanone 16 could be particularly useful as a starting material en route to Ia – c , X 2 = CO 2 H, because of the furan ring, which can be converted into the carboxy group 10…”

“…In the first step, the hydroxyalkyl group and two stereogenic C atoms of Ia – c are established through regio‐ and stereoselective reaction of IV with aldehydes, furnishing cycloalkenylsulfoximines III 6,8. In the second step, the amino‐substituted stereogenic tertiary carbon centre of Ia – c is set up through an intramolecular amination of the sulfoximine‐activated double bond of III by the carbamate method, leading to oxazinanone IIa 6c,9,10. Oxazinanone IIb , which is synthetically complementary to IIa , will be generated through sulfoximine displacement by halide.…”

Modular Asymmetric Synthesis of Functionalized Azaspirocycles Based on the Sulfoximine Auxiliary

“…18 This can be achieved by reaction with chloro-and iodoformic esters, respectively. Because of their potential conversion to the corresponding alkylzinc iodides 40 and ready cross-coupling reaction 27 , we decided to synthesize the iodo derivative 50 (Scheme 20). …”

KOH-catalyzed regioselective ring openings of N-tosylaziridines with malonates in acetone

“…Their synthetic utility as well as interesting biological activities has led many researchers to develop more interesting and efficient routes toward their transformation [4][5][6][7][8][9][10][11]. In recent years, some attractive strategies for the stereoselective synthesis of ␥-amino acids have been gradually reported.…”