Process for the selective enzymatic hydroxylation of...

Details Process for the selective enzymatic hydroxylation of... Process for the selective enzymatic hydroxylation of...

1999-09-17

2001-09-11

Padmanabhan, Sreeni (Department: 1621)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Preparing oxygen-containing organic compound

C435S147000, C435S148000, C435S832000, C568S343000, C568S376000, C568S379000, C568S420000, C568S626000

Reexamination Certificate

active

06287829

ABSTRACT:

The present invention relates to a process for the selective hydroxylation of aldehydes. and ketones using enzymes or microorganisms
TECHNOLOGICAL BACKGROUND
Hydroxylated aldehydes and ketones are of great industrial importance as synthesis intermediates. Thus, DE 36 22 839 discloses the synthesis, using hydroxylated ketones, of compounds having cardiac activity.
WO 86/07611 discloses the synthesis of 4-hydroxycyclopent-2-en-1-one and 3-hydroxycyclopentanone. These compounds are used in the preparation of prostaglandins.
A further area of application is the preparation of compounds for liquid crystal compositions (F. Hoffman-La Roche, Calif. 113:58558, Jpn. Kokai Tokkyo Koho JP 02 25,451 [90.25,451]).
Linking a hydroxyl group to a non-activated carbon atom is a very difficult task if merely “conventional” chemical methods are used therefor. Apart from recently published work using what are termed Gif systems (D. H. R. Barton and W. Chavasiri; Tetrahedron., 1994, 50, 19; D. H. R. Barton and R. D. Doller, Acc. Chem. Res., 1992, 25, 504), there are no purely chemical regioselective methods for hydroxylating non-activated carbon atoms. However, using these Gif systems, hydroxylation could not be performed enantioselectively either. In addition, the yield is so low that these processes are not useful for industrial implementation.
It is not only of importance to position the hydroxyl group regioselectively on a certain carbon atom relative to the carbonyl group. Generally in the course of the hydroxylation a new chiral center is formed. In particular as an intermediate for pharmaceuticals, but also for the agrochemical and cosmetics area, it is of importance that one of the two enantiomers or diastereomers is formed preferentially.
Chemical methods for enantioselective hydroxylation are only available for the &agr;-carbon atom. These are preferably reactions via corresponding enolates, where via suitable complexation using chiral auxiliaries, a certain enantioselectivity is achieved. A disadvantage of using these enantiomer-enriched &agr;-hydroxycarbonyl compounds, is, however, that racemization occurs readily at the &agr;-carbon.
The enzymatic hydroxylation is therefore the only method for solving the set object of the enantioselective hydroxylation of aldehydes and ketones. In this case, especially, numerous examples of hydroxylation of steroides are known, where, as result of the rigid molecular structure, with suitable choice of enzymes or microorganisms, both good regioselectivities and good stereoselectivities were achieved. These reactions are used industrially for the synthesis of pharmaceutically active intermediates.
However, there is no general method for enzymatic hydroxylation of aldehydes and ketones. One reason for this is that, due to the oxidoreductases present in all microorganisms, the carbonyl group itself is reduced, with hydroxylation frequently no longer occurring at all.
With the aid of the concept of the reversible anchor/protecting group, it is possible to carry out a regioselective hydroxylation with chemical yields of up to 70%. This concept is based- on derivatizing the carbonyl group, as result of which it is protected from the biotransformation due to the oxidoreductases. In addition, it is possible to model the chemical and physical properties of the substrate via this protecting group and thus, for example, to decrease the volatility which is interferring for some processes or to introduce a chromophore which is necessary for some chromatographic separations. Suitable anchor/protecting groups are, especially, acetals, aminoacetals, mercaptals or aminals. After carrying out the enzymatic hydroxylation, these protecting/anchor groups are removed again under mild conditions. Hitherto, only non-chiral protecting/anchor groups have been used, as disclosed, for instance, in Chem. Abstr. 125(1), 1996: 10221, which describes the enzymatic hydroxylation of cyclic ketones using the enzyme from Beauveria bassiana ATCC 7159 and the non-chiral N-benzoyl derivative of aminoethanol as protecting group. Although high chemical yields have been achieved, the enantionmeric excess is a maximum of 40% (Biohydroxylation as the Key Step in the Synthesis of Optically Active 3-Substituted Cyclopentanone Derivatives; G. Braunegg, A. de Raadt et al., BIOTRANS '95, University of Warwick, Coventry, Sep. 5-8, 1995, UK).
Owing to the constantly increasing requirement for optically pure hydroxylated oxo compounds, it is desirable to provide processes which are suitable for preparing these compounds in a high optical yield.
Surprisingly, it has now been found that when chiral protecting/anchor groups are used, both the chemical yield and also the enantiomeric excess can be increased considerably.
The invention therefore relates to a process for preparing compounds of the formula
where in the formula II one of the radicals X, Y is hydrogen,
n is one of the integers 0, 1, 2 or 3, where the compounds of the formula I may contain a double bond in the cycle, and
m is one of the numbers 0 or 1,
Z
1
and Z
2
independently of one another are a C
1
- to C
8
-alkylene radical, which may optionally be substituted by C
1
- to C
4
-alkyl and/or be unsaturated,
R
1
, R
2
independently of one another are hydrogen or unbranched or branched or Cyclic C
1-4
-alkyl or R
1
and R
2
together with the cycle containing the group A form a bicyclic compound of the structure bicyclo [a, b, c] heptane to decane (a, b, c=0, 1, 2, 3 or 4), which ray optionally be substituted by C
1
-C
4
-alkyl and/or be unsaturated, and
R
3
, R
4
may be hydrogen or an unbranched, branched or cyclic C
1
-C
8
-alkyl,
which comprises a compound of the formula
where A, A′, R
1
, R
2
, R
3
, R
4
, Z
1
, Z
2
, m and n have the above meaning, being protected with a chiral, aliphatic, cyclic or heterocyclic diol, amino alcohol, acetal, aminoacetal, mercaptol or aminal as anchor/protecting group,
the compound protected in this manner being enzymatically regioselectively and stereoselectively hydroxylated,
the hydroxyl group being optionally protected with a suitable compound and the anchor/protecting group being removed.
A compound of the formulae (III) or (IV) can be, for example, one of the following
Other suitable compounds of the formula III or IV are, for example
bicyclo [2.2.1]heptan-2-one
(1R) and (1S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one
trans-1-decalone
2-decalone
(1S) and (1R)-1,3,3-trimethylbicyclo[2.2.1]heptan-2-one
bicyclo[3.3.0]octane-3,7-dione
bicyclo[3.3.0]octan-3-one
bicyclo[3.3.0]oct-7-en-2-one
bicyclo[3.3.0]oct-6-en-2-one
bicyclo[4.2.0]oct-2-en-7-one
bicyclo[3.2.0]hept-2-en-7-one
bicyclo[3.2.0]hept-2-en-6-one.
Protecting/anchor groups which can be used are, especially, chiral acetals, aminoacetals, mercaptals or aminals. These may be cyclic or non-cyclic. Preferably, these are 1,2- and 1,3-diols, amino alcohols, dithiols and aminodiols, and also 1,2- and 1,3-diamines. These must have at least one chiral center. These compounds can be aliphatic, alicyclic or heterocyclic. In addition, it is possible that these protecting/anchor groups bear other functional groups, in addition to those groups which are required for the fixing to the substrate molecule.
A preferred anchor/protecting group is a compound of the formulae
where R′ is unbranched or branched C
1-4
-alkyl, that is, for example, the N-benzoyl derivatives of (R)-2-amino-1-propanol, (S)-2-amino-1-propanol, (R)-1-amino-2-propanol, (S)-1-amino-2-propanol, (R)-2-amino-1-butanol, (S)-2-amino-1-butanol, (R)-1-amino-2-butanol or (S)-1-amino-2-butanol.
After the enzymatic hydroxylation is carried out, these protecting/anchor groups are then removed again under mild conditions. The cleavage can be carried out using standard chemical methods (T. W. Greene P. G. M. Wuts, “Protective Groups in Organic Synthesis”, John Wiley & Sons, Inc 1991), such as by acid-catalyzed hydrolysis, electrolysis or by using metal salts.
M

Affiliated with

Also associated with

Rating

Process for the selective enzymatic hydroxylation of... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for the selective enzymatic hydroxylation of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the selective enzymatic hydroxylation of... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2526448