Synthesis of capsaicin derivatives

A method of preparing a 6-heptyne derivative of capsaicin of the following formula 1,

• wherein:
• R is a substituent selected from the group consisting of a C1-C18 straight chain or branched alkyl, a C2-C18 straight chain or branched alkenyl, a C2-C18 straight chain or branched alkynyl, trifluoromethyl, a C3-C12 cycloalkyl, phenoxy, phenylthiol, fluoro, chloro, bromo, iodo and an optionally substituted phenyl ring;
• wherein the optionally substituted phenyl ring is optionally substituted in any position with 1-5 identical or different substituents selected from the group consisting of fluoro, chloro, bromo, iodo, cyano, nitro, trifluoromethyl, a C1-C6 straight chain or branched alkoxy, a C1-C6 sulfoxy, a —S—C1-C6 alkyl, a C1-C6 straight chain or branched alkyl, a C2-C6 straight chain or branched alkenyl, a C2-C6 straight chain or branched alkynyl, a C1-C6 fluoroalkyl, a C1-C6 chloroalkyl, a C1-C6 bromoalkyl, a C1-C6 iodoalkyl, a COO—C1-C6 alkyl, a CONH(C1-C6 alkyl) and a CON(C1-C6 alkyl)2;
• and
• R′ is 0-5 identical or different substituents, in any one or more positions, selected from the group consisting of fluoro, chloro, bromo, iodo, hydroxy, cyano, amino, nitro, trifluoromethyl, a C1-C6 straight chain or branched alkoxy, a C1-C6 sulfoxy, a —S—C1-C6 alkyl, a C1-C6 straight chain or branched alkyl, a C2-C6 straight chain or branched alkenyl, a C2-C6 straight chain or branched alkynyl, a C1-C6 fluoroalkyl, a C1-C6 chloroalkyl, a C1-C6 bromoalkyl, a C1-C6 iodoalkyl, COOH, CONH2, a —NHCO(C1-C6 alkyl), a COO—C1-C6 alkyl, a CONH(C1-C6 alkyl) and a CON(C1-C6 alkyl)2;
• the method comprising a step of:
• coupling a compound of the following formula 3 with a benzylamine of the following formula 2 or any suitable salt thereof, wherein R and R′ in formula 2 and formula 3 are as defined in formula 1,
• using 1,1′-carbonyldiimidazole (CDI).