4.4- Dimethylpentanoic acid

A chemist in need of 2,2-dimethylpentanoic acid decided to synthesize some by reaction of 2-ch.loro-2-methylpentane with NaCN, followed by hydrolysis of the product. After the reaction sequence vvas carried out, however, none o the desired product could be found. What do you suppose went wrong ... 

Enantiomerically pure (2, 35)-3-hydroxy-2,4-dimethylpentanoic acid is liberated by a Bacycr-Villigcr oxidation which occurs in a nonrcgiosclcctivc manner. Furthermore, the chiral auxiliary information is lost in the final step ( immolative method )41. 

S,4S,5 E,7E)-3-Amino-4-hydroxy-6-methyl-8-(4-bromophenyl)-octa-5,7-dienoic acid [Aboa = Br-Ahmp, Br-Apoa], (2S,3S,8S,9S)-3-Amino-9-methoxy-2,6,8-trimethyl-10-phenyl-deca-4,6-dienoic acid (Adda). 3-Amino-2,4-dimethylpentanoic acid (Admpa). (2S,3R,5S)-3-amino-2,5,9-trihydroxy-10-phenyldecanoic acid (Ahda). j3-Aminoisobutyric acid (jS-AiB). (3S,4S,5E,7E)-3-Amino-4-hydroxy-6-methyl-8-phenylocta-5,7-dienoic acid [Ahmp (Faulkner) or Apoa (Fusetani)]. (2S,3R,5R)-3-Amino-2,5-dihydroxy-8-phenyloctanoic acid (Ahoa). 3-Aminopentanoic acid (Apa /5-Apa). (2R,3R)-3-Amino-2-methylbutanoic add (Amba). 3-Amino-2-methylhexanoic acid (Amha). 3-Amino-2-methyl-7-octynoic add (Amoa, Amoya). 3-Amino-7-octynoic add (Aoya). (2S,3R)-3-Amino-2-methylpentanoic acid (Map). http // www.ncbi.nlm.nih.gov/ Taxonomy/ tax.html... 

The lactone of 2,4-dihydroxy-3,3-dimethylpentanoic acid (known as pantolactone) has been successfully employed as a chiral auxiliary in several D-A reactions. For example, in conjunction with TiCl4, it provides a 92% de in the reaction of 2,3-dimethylbutadiene with a-cyanocinnamic acid. The diastereoselectivity is consistent with a chelated structure similar to that shown above for acryloyl lactate. In the absence of TiCl4, this same ester gives a 64% de of the opposite configuration. This... 

In part (3) t-butyllithiura is first produced. It is reacted with ethylene and subsequently carbonated to yield 4,4-dimethylpentanoic acid. 

Ring contraction. Cyclohexene added dropwise at 10-12° during 55 min. from a syringe to AggO in 98%-H2S04 under 1 atm. CO 1-methylcyclopentane-carboxylic acid. Y 84%. - Similarly 1-Hexanol a,a-dimethylpentanoic acid. Y 79%. F. e., also from satd. hydrocarbons, s. Y. Souma and H. Sano, Bull. Chem. Soc. Japan 47, 1717 (1974). 

---