Methyl 2-pentynoate

Mori started with the early introduction of the chiral centre [298] in using (3-oxidation of pentanoic acid A by the yeast, Candida rugosa, IFO 0750 [299]. The obtained (R)-3-hydroxypentanoic acid B was transformed into C in a few conventional steps. The second building block was prepared from methyl 2-pentynoate D conjugate addition of lithium dimethyl cuprate yielded E, which was further converted into the frans-configured vinyl bromide F. Hydro-boration of C yielded G which upon Suzuki s palladium catalysed cross-coupling with F furnished 157 after treatment of the reaction product with hydrochloric acid followed by chromatographic purification. The synthesis of ent-157 used (S)-3-hydroxypentanoic acid. 

Pentane, 1,1-diphenyl-, 55, 10 2-Pentynoic acid, methyl ester, 55, 76 Peracetic acid [Ethaneperoxoic acid], 55, 87 88... 

Pentynoic acid, 5-hydroxy-, 56, 51 2-Pcntynoic acid, methyl ester 55, 76 Peptides, 56, 88 Peracetic acid, 55, 87, 88 Perbenzoic acid, m-chloro-, 55, 88 Perbenzoic acid, 3-chloro-, 56, 1 Peroxydisulfunc acid ([(HO)S-(0)2 ] 2 Ot), diammomum salt, 56, 69 PHASE TRANSFER ALKYLATION, 55,... 

The translational activity of various unsaturated analogs of L-isoleucine was evaluated using an Escherichia coli strain auxotrophic for isoleucine. It was observed that the alkene [2-amino-3-methyl-4-pentenoic acid (2)] and alkyne [2-amino-3-methyl-4-pentynoic acid (3)] derivatives of L-isoleucine can support protein synthesis at levels approximately 50% of that observed in cultures supplemented with isoleucine. However, no incorporation of the ocC or /JC methylated derivatives could be detected. In order to examine the stereoselectivity of incorporation, the (2S, 3S) and (2S, 3R) diastereomers of 2 and 3 were prepared. The extents of isoleucine substitution in vivo were 80% and 70% for (2S, 3S)-2 and (2S, 3S)-3, respectively, under the conditions examined in this study. 

Diastereomers mixtures (Figure 1) of 2-amino-3-methyl-4-pentenoic acid (2), 2-amino-2-methyl-4-pentynoic acid (21), 2-amino-3-dimethyl-4-pentenoic acid (22), 2-amino-2,3-dimethyl-4-pentenoic acid (23), 2-amino-3-methyl-4-pentynoic acid (3), 2-amino-3-dimethyl-4-pentynoic acid (31), 2-amino-2,3-dimethyl-4-pen-tynoic acid (32) were prepared according to Aidene et al.tl The regioselective reaction between a-unsaturated organozincs and A-(phenylsulfanyl)iminoesters was used as a starting step to obtain the a-aminoesters.11... 

The oxypalladation-reductive elimination of 3-pentynoic acid with 1-bromo-l-heptyne has also been described (Scheme 22). However, 4-methyl-4-(l-heptynyl)-5//-furan-2-one was isolated in low yield. Substitution of 1-iodo-l-heptyne for 1-bromo-l-heptyne resulted in the formation of the diyne derivative as the only reaction product. Most probably, the diyne derivative is formed via Pd-catalyzed coupling of the l-halo-l-aUcyne. 

By reduction of methyl 3-oxo-4-pentynoate (229) (Fig. 59) gave the corresponding (5)-3-hydroxy ester 230 (80% e.e.) whereas its 5-trimethylsilyl derivative 231 gave the enantiomer 232 [349]. 

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