Organoboron amino acids

Bombykol is an estrogenic hormone ((I0E,12Z)-hexadecadiene-l-ol) which induces sexual excitement in a male silkworm. Bombykol is prepared by the hydroboration of acetylene compounds with a catecol boron compound and a cross coupling reaction with palladium catalyst, etc., as shown in Scheme 6.4 [41—47], The organoboron compounds are used for leucotriene intermediates [48], L-ribose and amino acids [47], etc., as the others. 

The Petasis reaction represents a boronic acid variant of the Mannich reaction, and therefore is also referred to as a borono-Mannich reaction. It was first explored with formaldehyde as the carbonyl component and alkenyl, or ot,p-unsaturated organoboronic acid (III) as a nucleophile (route a in Scheme 8.2) [13]. It was later developed in a practical synthesis of a-amino acids (VI) from ot-keto acids (IV) and alkenyl boronic acids (III) [14] (route b in Scheme 8.2). 

Condensation reactions between o-amino(or hydroxy)-benzenecarboxy-acids (or amides) and B(NMe2)3, PhB(NMe2)2, or PhBClg give organoboron heterocycles (78) containing a carbonyl group in a / -position to an annular... 

Petasis NA, Zavialov lA (1998) Highly Stereocontrolled One-Step Synthesis of antibeta -Amino Alcohols from Organoboronic Acids, Amines, and alpha -Hydroxy Aldehydes. J Am Chem Soc 120 11798-11799... 

Asymmetric addition of 4-chlorophenylboronic acid (2u) to a,P-unsaturated y-amino ester (26a), followed by deprotection and ester hydrolysis gave optically active 4-amino-3-(4-chlorophenyl)butyric acid (Baclofen) hydrochloride (Scheme 4.10), which plays an important role in various nervous system functions. The best result was observed with a large excess of organoboronic acids (5.0 equiv to 26a) in a 10 1 dioxane-water mixture containing aqueous cesium carbonate [24]. 

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