Tetrahydroprotoberbine compounds and uses thereof in the treatment of neurological, psychiatric and neurodegenerative diseases

1. A method of increasing dopamine release in the prefrontal cortex comprising administering to a subject in need thereof an effective amount of a compound of formula (I):

or a pharmaceutically acceptable salt, solvate or prodrug thereof, wherein:

R1 and R2 are independently H, alkyl, benzyl or —COR9; or R1 and R2 together form (CH 2 ) m ;

R4 is H, alkyl, benzyl, or —COR9;

R3 is H or OR10, wherein R10 is H, alkyl, benzyl or —COR9, or R10 taken together with R4 forms (CH 2 ) m ;

R5 is H or OR11, wherein R11 is H, alkyl, benzyl or —COR9, or R11 taken together with R4 forms (CH 2 ) m ;

R6 is H or halogen;

R9 is H or alkyl;

m is 1 or 2, and

wherein when R10 taken together with R4 forms (CH 2 ) m , then R5 is H or OR11,

wherein R11 is H, alkyl, benzyl or —COR9, and

wherein when R11 taken together with R4 forms (CH 2 ) m , then R3 is H or OR11,

wherein R11 is H, alkyl, benzyl or —COR9, and

wherein at least one of R3 and R5 is other than H.

2. The method according to claim 1 , wherein the increasing dopamine release in the prefrontal cortex is effective in the treatment of cognitive impairment arising from hypodopamine function associated with the related conditions of schizophrenia and major depression.

3. The method according to claim 1 , wherein the compound is administered in conjunction with one or more other therapeutic agents.

4. The method according to claim 1 , wherein R3 is H and R5 is OR11.

5. The method according to claim 1 , wherein R5 is H and R3 is OR10.

6. The method according to claim 1 , wherein

R1 and R2 are independently H or alkyl, or R1 and R2 together form (CH2) m ;

R5 is H or O-alkyl;

R6 is H or halogen;

R7 is H;

R8 is H or alkyl; and

either R3 is H or O-alkyl, and R4 is H, or

R3 is OR10 and R10 and R4 together form (CH2) m .

7. The method according to claim 1 , wherein

R1 and R2 are independently H or alkyl, or R1 and R2 together form (CH2) m ;

R3 is H or O-alkyl;

R6 is H or halogen;

R7 is H;

R8 is H or alkyl; and

either R4 is H, and R5 is H or O-alkyl, or

R5 is OR11 and R11 and R4 together form (CH2) m .

8. The method according to claim 1 , wherein

R1 and R2 are independently H or alkyl;

R3and R5 are independently H or O-alkyl;

R4 and R7 are H;

R6 is H or halogen; and

R8 is H or alkyl.

9. The method according to claim 1 , wherein

R1 and R2 are independently H or alkyl;

R3 and R5 are independently H or O-alkyl;

R4, R6 and R7 are H; and

R8 is H or alkyl.

10. The method according to claim 1 , wherein each alkyl is a C 1 -C 4 alkyl.

11. The method according to claim 1 wherein administration involves an effective amount of enantiomerically pure d-govadine derived from a process comprising the steps:

(a) performing a coupling reaction between compounds (XVI) and (XVII) to provide amide (XVIII);

(b) performing a Bischler-Napieralski reaction on the amide (XVIII) to provide dihydroisoquinoline intermediate (XIX);

(c) reducing the dihydroisoquinoline intermediate (XIX) with a chiral catalyst to provide compound (XIV) or (XV);

(d) performing a Mannich-type cyclization on compound (XIV) or (XV) to obtain d- or I-govadine,

wherein the synthesis route is as follows:

and wherein X is CI or OH, and R12 is a protecting group

or wherein X is OH, and the coupling reaction is a thermal coupling reaction in the presence or absence of solvent; wherein the Bischler-Napieralski reaction uses POCI 3 ; wherein the chiral catalyst is Noyori's catalyst; wherein the Mannich-type cyclization is a Pictet-Spengler cyclization and wherein the synthesis route is as follows:

12. The method according to claim 1 , wherein the compound is