Sulfonyl camphor

The most important group of derivatives for the amino function (Fig. 7-4) is the carbamate group, which can be formed by reactions with acids, acid chlorides or acid anhydrides. A series of chlorides as 2-chloroisovalerylchloride [1], chrysanthe-moylchloride [2] and especially chloride compounds of terpene derivatives (cam-phanic acid chloride [3], camphor-10-sulfonyl chloride [4]) are used. The a-methoxy-a-trifluoromethylphenylacetic acid or the corresponding acid chloride introduced by Mosher in the 1970s are very useful reagents for the derivatization of amines and alcohols [5]. 

Scheme 3.50 Camphor-derived A -sulfonylated amino alcohol ligand for additions of ZnEt2 to aldehydes.

Gotti et al. [42] reported an analytical study of penicillamine in pharmaceuticals by capillary zone electrophoresis. Dispersions of the drug (0.4 mg/mL for the determination of (/q-penicillaminc in water containing 0.03% of the internal standard, S -met hy I - r-cystei ne, were injected at 5 kPa for 10 seconds into the capillary (48.5 cm x 50 pm i.d., 40 cm to detector). Electrophoresis was carried out at 15 °C and 30 kV, with a pH 2.5 buffer of 50 mM potassium phosphate and detection at 200 rnn. Calibration graphs were linear for 0.2-0.6 pg/mL (detection limit = 90 pM). For a more sensitive determination of penicillamine, or for the separation of its enantiomers, a derivative was prepared. Solutions (0.5 mL, final concentration 20 pg/mL) in 10 mM phosphate buffer (pH 8) were mixed with 1 mL of methanolic 0.015% 1,1 -[ethylidenebis-(sulfonyl)]bis-benzene and, after 2 min, with 0.5 mL of pH 2.5 phosphate buffer. An internal standard (0.03% tryptophan, 0.15 mL) was added and aliquots were injected. With the same pH 2.5 buffer and detection at 220 nm, calibration graphs were linear for 9.3-37.2 pg/mL, with a detection limit of 2.5 pM. For the determination of small amounts of (L)-penicillamine impurity, the final analyte concentration was 75 pg/mL, the pH 2.5 buffer contained 5 mM beta-cyclodextrin and 30 mM (+)-camphor-10-sulfonic acid, with a voltage of 20 kV, and detection at 220 nm. Calibration graphs were linear for 0.5-2% of the toxic (L)-enantiomer, with a detection limit of 0.3%. 

Davis et al.111 developed another method for reagent-controlled asymmetric oxidation of enolates to a-hydroxy carbonyl compounds using (+)-camphor-sulfonyl oxaziridine (147) as the oxidant. This method afforded synthetically useful ee (60-95%) for most carbonyl compounds such as acyclic keto esters, amides, and a-oxo ester enolates (Table 4-20). 

This chiral peracid oxidation was used to convert the vinyl sulfide 3, derived from (S)-( + )-camphor-10-sulfonyl chloride, to a chiral sulfoxide (96 4 selectivity),... 

The enantioselective addition of diethylzinc to aromatic aldehydes has been performed in the presence of an IV-sulfonylated amino alcohol-Ti(0-/-Pr)4 catalytic system.113 In the presence of (42), excellent enantioselectivities (up to 94% ee) have been obtained. The study revealed that the steric bulk of the camphor group does not affect the stereocontrol. 

Z-camphor-10-sulfonyl chloride, (e) Z-menthoxy- and d-bomoxyacetic acids, (/) Z-menthylglycine, and (g) d-tartranilic acid. 

W. Oppolzer and R. N. Radinov, Tetrahedron Letters, 29, 5645 (1988). Camphor-10-sulfonyl chloride. 

Camphor-lO-sulfonyl chloride Chrysanthemic acid chloride (l,T-Binaphthalene)-2,2 -diol Camphor... 

The enantiomeric purity of the bicyclic 3,6-dihydro-277-l,2-oxazine 3 was determined by H NMR of the D-camphor-10-sulfonyl derivative and was found to be >95%. The configuration of this compound was assigned by comparison with the reported optical rotation data, as (1 S,4R). This synthetic approach was utilized in the enantioselective synthesis of conduramine and streptamine analogs91. 

A number of substituted cyclic and acyclic 1,3-dienes have also been reacted, and the absolute configuration of the products assigned129. The enantiomeric excess of the dihydro-1,2-oxazines was determined by H-NMR or GC analysis of the corresponding derivatives prepared with both ( + )-camphor-10-sulfonyl chloride or (S )-3,3,3-trifiuoro-2-methoxy-2-phenylpropanoyl chloride (Table l)96-96. 

Hydroxylation of the sodium enolate of lactone (16) with (+)-( ) gives a-hydroxy lactone in 77% ee (eq 17). Kinetic resolution and asymmetric hydroxylation with (camphor-sulfonyl)oxaziridines has been applied to the synthesis of enantiomerically enriched a-hydroxy carbonyl compounds having multiple stereocenters, which may otherwise be difficult to prepare. Thus hydroxylation of the enolate of racemic 3-methylvalerolactone with substoichiometric amounts of (—)-(l) affords (25,3/J)-verrucarinolactone in 60% ee (eq 18) which on recrystallization is obtained enantiomerically pure. ... 

Preparation of the Auxiliary. A synthesis of the (1/ ) auxiliary has been reported starting from (-i-)-camphor (eq 1). Zinc reduction of the intermediate imine (2) followed by sulfonylation and ketone reduction with Ca(B 114)2 afforded the cis.endo product in 70-75% overall yield from camphorquinone (1). 

D-Camphor-lO-sulfonyl chloride can be prepared from commercially available D-camphor-lO-sulfonic acid and phosphorus pentachloride or thionyl chloride. The checkers used the following procedure. D-Camphor-lO-sulfonic acid (50.0 g.) was added slowly to 50 g. of thionyl chloride. The mixture was boiled under reflux until homogeneous and then for a further 2 hours. The solution was cooled and poured onto ca. 500 g. of... 

Recently there was a report on the asymmetric synthesis of diaziridines. For example, on reaction of camphor-sulfonylated acetone-oxime with methylamine, optically active 115 is formed with an optical purity of 10%... 

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