Amino adds synthons

The /3-amino add (S)-ethyl-3-amino-4-pentynoate is a chiral synthon used in the synthesis of xemilofiban hydrochloride, an anti-platelet agent. (R)- and (S)-enanti-omers of ethyl 3-amino-4-pentynoate were obtained in enantiomerically pure form by employing penicillin acylase (Pen G acylase, PGA, Chapter 7, Section 7.5.1) (Figure 13.32) (Topgi, 1999). Both the acylation and deacylation modes were ap-... 

Cooke and coworkers reported on the synthesis of the amino add N-berizyl -4-acetylproline (2-889) (Scheme 2.198) [453], as this might represent an interesting synthon for the preparation of bioactive compounds. These authors also used a domino iminium ion formation/aza-Cope/Mannich protocol. Thus, treatment of the secondary amine 2-885 with glyoxylic acid (2-888) primarily provided the corresponding iminium ion, which led to 2-889 in 64% yield as a mixture of diastereom-ers. 

Tisler, M., Kolar, P., Amino Adds as Synthons for Heterocyclic Compounds, 64, 1. 

Treat the resin in each of the 31 vessels with a unique R Fmoc-amino acid synthon. For example, add a solution of Fmoc-L-alanine (50 mg, 0.16 mmol,... 

The reduction of trifluoromethylimines with Mg(0) affords A-silyl difluoroena-mines." These synthons are very interesting for the preparation of difluoro- S-amino alcohols and of difluoro amino acids (cf. Chapter 4). They can also add onto radicals, react with sulfur ylides to afford difluoromethylaziridines, or even undergo intramolecular ene reactions (Figure 2.26)." ... 

L. W. Parker, and J. J. Venit, Biocatalytic preparation of a chiral synthon for a vasopeptidase inhibitor enzymatic conversion of N2-[N-phenylmethoxy)carbo-nyl] L-homocysteinyl]- l-lysine (1,1 J-disulfide to 4S-(4/,71,10aJ)]-l-octahydro-5-oxo-4-[phenylmethoxy)carbonyl]amino]-7H-pyrido-[2,l-b][l,3]thiazepine-7-carboxylic add methyl ester by a novel l -lysine e-aminotransferase, Enzyme Microb. Technd. 2000, 27, 376-389. 

Trimethylsilyl cyanide is a useful reagent for the preparation of /8-amino alcohols,2 a-amino nitriles,3 and a-trimethylsiloxyacrylo-nitriles4 from the corresponding ketones, imines, and ketenes. The reagent adds rapidly to the carbonyl of aldehydes at 25°C,2 and the resulting adducts have proven useful precursors for the preparation of carbonyl anion synthons.5 Enones give exclusively the products derived from 1,2-addition.2... 

The third reaction pattern in nucleophilic reaction to difluoroalkenes is addition. Protic nucleophiles such as amines and alcohols add sometimes to the difluoroalkenes in a manner of 1,2-addition to the double bond where both nucleophilic moiety and proton are incorporated into the double bond (Scheme 2.27). A difluoromethylene moiety is potentially a carbonyl synthon and a difluoroalkylidene moiety is a synthon of an amide [17] and an ester (53) [18]. l,l-Difluoro-2-aminoalkenes (52) (R1 = amino moiety) would be transformed to dipeptides (53) (RX = amino ester, R1 = amino moiety) on reacting with amino esters. This idea was realized by the reaction of 60 with a variety of amino esters, leading to a practical synthesis of trifluoroalanine dipeptides (62) as shown in Scheme 2.27 [ 19]. 

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