Novel steroid saponin compounds (XR-1) and (XR-2) are extracted from Solanam aculeatissimum, a plant belonging to the Solanum genus, and 16-dehydropregnenolone is obtained by hydrolyzing the said compounds, subjecting the hydrolyzed product to Marker's degradation, and treating the obtained product with aqueous alkali.

DESCRIPTION 
FIELD OF THE INVENTION 
The present invention relates to novel steroid saponins obtained from 
plants belonging to Solanaceae, extraction of the said steroid saponins 
and process for preparing 16-dehydropregnenolone or its ester from the 
said steroid saponins. 
BACKGROUND OF THE INVENTION 
Said 16-dehydropregnenolone is a compound having the following formula: 
##STR1## 
and is useful as an intermediate for preparing various sexual hormones, 
corticoids, oral contraceptive drugs etc. It is known that 
16-dehydropregnenolone is prepared from diosgenin which is contained 
mainly in plants of the genus Dioscorea. However, Dioscorea tokoro and 
some other analogous species, which are the diosgenin containing plants 
growing in Japan, are not satisfactory source of supply for diosgenin 
because their rhizomes are poor and contents of diosgenin are less than 
only 1%. The chief source of diosgenin at the present time is Dioscorea 
composita (barbasco) which is a naturally growing species in Mexico. 
However, this species is not reliable source because it is a wild plant. 
It has therefore been felt anxious about deficiency of diosgenin source 
and found necessary to develop a novel preparative method for 
16-dehydropregnenolone from other source. 
DISCLOSURE OF THE INVENTION 
As a result of an extensive study searching for steroid saponin containing 
plants which may be a source for the preparation of 16-dehydropregnenolone 
carried out by the present inventors, it has now been discovered that 
Solanum species belonging to Solanaceae, typically Solanum aculeatissimum 
Jacq., contains steroid saponin compounds represented by formulae (XR-1) 
and (XR-2) described later in a high content, that these compounds can be 
successfully extracted, and that 16-dehydropregnenolone can be prepared 
using these compounds as starting materials.

According to the invention, there are provided (1) a compound represented 
by the following formula (XR-1): 
##STR2## 
(2) a compound represented by the following formula (XR-2): 
##STR3## 
(3) a process for extracting the compounds (XR-1) and (XR-2) which 
comprises extracting a plant belonging to the Solanum genus and containing 
the compounds (XR-1) and (XR-2) with water or an organic solvent and 
separating the compounds (XR-1) and (XR-2) contained in the extract, and 
(4) a process for preparing 16-dehydropregnenolone or lower aliphatic acid 
ester thereof which comprises hydrolyzing the compound (XR-1) or (XR-2), 
subjecting the obtained product to Marker's degradation and treating the 
obtained product with water, a lower alcohol or a lower aliphatic acid. 
In the process for extracting the compounds (XR-1) and (XR-2), it is 
preferable to use water or a hydrophilic organic solvent, especially 
water, a lower alcohol (such as for example, methanol, ethanol, propanol 
etc.) or a mixture thereof. The compounds (XR-1) and (XR-2) can be 
obtained in an isolated state, or as a mixture of these two compounds, by 
treating the said extract, or extract (organic phase) obtained by 
extracting the concentrate of the said extract with other solvent (for 
example, a mixture of water: butanol=1:1), with the conventional means 
such as concentration, crystallization, recrystallization, chromatography, 
solvent-partition etc. Since both the compounds (XR-1) and (XR-2) can be 
used for preparing 16-dehydropregnenolone in the same way, it is not 
necessary to separate these two compounds and it is more preferable to use 
as a mixture of the two compounds. 
The compounds (XR-1) and (XR-2) have the following physical properties when 
they are isolated. 
XR-1 
colorless needles 
m.p.: 196.degree.-204.degree. C. 
angle of rotation: [.alpha.].sub.D.sup.27 =-28.4.degree. (c=1.02, pyridine) 
FD-MS (m/Z): 1069 
IR .nu..sub.max.sup.KBr (cm.sup.- 1): 3400 
CMR (d.sub.5 -py.) 
.delta.(ppm)=15.03, 16.11, 18.25, 18.40, 19.33, 21.04, 24.31, 30.06, 31.63, 
32.16, 32.16, 33.09, 33.77, 37.04, 37.48, 38.56, 38.85, 39.83, 40.46, 
50.22, 56.42, 61.35, 62.42, 62.62, 69.25, 70.28, 71.55, 72.18, 72.18, 
72.48, 72.48, 73.60, 73.89, 75.11, 76.28, 77.21, 77.75, 78.10, 78.10, 
78.10, 78.10, 78.97, 80.87, 83.75, 100.15, 101.76, 102.69, 105.08, 120.11, 
121.68, 140.70 
XR-2 
angle of rotation: [.alpha.].sub.D.sup.28 =-57.7.degree. C. [c=0.75, 
methanol:water (1:1 V/V)] 
FD-MS (m/z): 1085, 1069 
IR .nu..sub.max.sup.KBr (cm.sup.-1): 3400 
CMR (d5-py.) 
.delta.(ppm)=15.08, 16.15, 18.45, 19.38, 21.13, 24.31, 30.11, 31.68, 32.16, 
32.16, 33.14, 33.82, 37.09, 37.48, 38.61, 38.61, 39.83, 40.51, 50.32, 
56.47, 61.69, 62.23, 62.42, 62.67, 69.25. 69.94, 71.60, 71.60, 72.18, 
72.57, 73.94, 74.72, 74.91, 75.16, 76.04, 77.26, 77.70, 78.14, 78.14, 
78.14, 78.14, 80.92, 83.80, 84.97, 100.44, 101.95, 105.13, 105.47, 120.16, 
121.57, 140.85 
In the process for preparing 16-dehydropregnenolone, the hydrolysis of the 
compound (XR-1) or (XR-2) is effected by treating the compound with 
mineral acid such as hydrochloric acid, sulfuric acid etc. in water, lower 
alcohol (methanol, ethanol, isopropanol etc.) or a mixture thereof. It is 
advisable to use the mineral acid in an amount exceeding the equimolar 
amount. The reaction is usually carried out by heating at a temperature 
around 70.degree. C. for 2 to 5 hours. By this hydrolysis are produced 
nuatigenin of the formula: 
##STR4## 
and isonuatigenin of the formula: 
##STR5## 
which is a secondary product. These compounds may be used in following 
steps as crude products, though they may be obtained in a pure state, for 
example, by subjecting the hydrolyzate to chromatography on silica gel 
column and eluting with a solvent such as a mixture of chloroform:methanol 
(100:100). 
Marker's degradation involves acetolysis and chromic acid oxidation (for 
example, Fieser & Fieser, "Steroids" page 549, 1959). 
The acetolysis is effected by reacting the above compounds with acetylating 
agent (acetic anhydride, acetyl chloride, 2,3-diacetoxypyridine etc.). 
This reaction may be carried out, for example, in two steps in which the 
said compounds are firstly reacted with an excess of the said acetylating 
agent in a solvent (acetic acid, pyridine, methanol, ethanol, isopropanol) 
at around 0.degree.-150.degree. C. (preferably room temperature to 
110.degree. C.) for 2-15 hours, and secondly reacted with acetic anhydride 
in a sealed tube at around 195.degree. C. for 18 hours. In this case, it 
is presumed that a mixture of the following two compounds is produced by 
the first step treatment. 
##STR6## 
These products in the first step may be used in the second step treatment 
after purifying, for example, by chromatography on alumina column (using a 
mixture of cyclohexane:benzene=7:3 as an eluent). The reaction may be 
accelerated by an acid (for example, toluenesulfonic acid) or a Lewis acid 
(for example, aluminum chloride). There may be used an organic acid (for 
example, octanoic acid) as a solvent. It is presumed that the following 
compound is produced in this reaction. 
##STR7## 
The chromic acid oxidation is effected by reacting the above acetolysis 
product with chromic anhydride. It is advisable to use chromic anhydride 
in an amount around three times the equimolar amount. As to the reaction 
conditions, a standing at around room temperature to 22.degree. C. for 
about an hour is sufficient. Reaction product may be separated, for 
example, by adding water to the reaction mixture and extracting the 
resulting mixture with ether. It is presumed that the following compound 
is produced in this chromic acid oxidation. 
##STR8## 
The above compound gives on treatment with water or a lower alcohol (for 
example, tert-butanol) in the presence of a base (for example, sodium 
hydroxide, potassium hydroxide) 16-dehydropregnenolone and on treatment 
with a lower aliphatic acid (for example, acetic acid) an aliphatic acid 
ester of 16-dehydropregnenolone. The treatment with water or the lower 
alcohol is usually carried out at 30.degree. C. for about 3 hours. The 
treatment with the aliphatic acid is usually carried out under reflux. 
Reaction product may be isolated by extraction with ether and 
chromatography on alumina column (using a mixture of 
cyclohexane:benzene=1:4 as an eluent). 
PREFERRED EMBODIMENTS OF THE INVENTION 
The invention will now be further illustrated by means of the following 
examples. 
EXAMPLE 1 
Extraction of the Compounds (XR-1) and (XR-2) 
Either 725 g of undried root or 290 g of dried root from Solanum 
aculeatissimum is extracted with methanol, denatured alcohol, ethanol or 
water. The liquid phase is concentrated under reduced pressure to give 
about 70 g of extract, from which fat is removed as required. The extract 
containing the compounds (XR-1) and (XR-2), thus obtained, may be used for 
preparation of 16-dehydropregnenolone without further treatment. 
EXAMPLE 2 
Preparation of 16-Dehydropregnenolone from a Mixture of the Compounds 
(XR-1) and (XR-2) 
(a) Hydrolysis 
To the extract obtained in Example 1 is added 700 ml of 2N-methanolic 
hydrochloric acid. The obtained mixture is heated under reflux for 2 
hours. After cooling, the mixture is neutralized with 5%--methanolic 
solution of sodium hydroxide or potassium hydroxide and evaporated under 
reduced pressure. The residue is used in the following steps without 
further treatment. Alternatively, the residue is treated with methanol to 
dissolve organic substances. Insoluble salts are removed by filtration and 
methanol is removed by distillation from the filtrate giving residue 
(about 24 g). 
(b) Marker's degradation 
The whole quantity of the residue obtained in (a) is dissolved in a small 
amount of pyridine and acetylated by adding about 230 ml of acetic 
anhydride and warming or standing overnight. The acetate, which is 
obtained on removing the solvent by distillation, is used with or without 
purification by column chromatography on alumina. The acetate is dissolved 
in 32 g of acetic anhydride. The obtained solution is heated at 
195.degree. C. for 18 hours in a sealed glass tube. After cooling, the 
seal is broken and 8 ml of water is added to the solution. A solution of 
6.7 g of sodium acetate in 200 ml of glacial acetic acid is added to the 
warmed solution, which was then cooled to 15.degree. C. A solution of 11 g 
of chromium trioxide in 43 ml of glacial acetic acid is added to the 
solution with stirring over a period of 15 minutes and allowed to react, 
while the temperature is kept constant at 15.degree. C. The mixture is 
left to stand for an hour keeping the temperature at 22.degree. C. and 
partitioned between water and ether (or ethyl acetate or other suitable 
solvent). The upper phase is concentrated to give a syrupy substance. 
(c) Treatment with an aqueous alkali solution 
To the syrupy substance are added 500 ml of tertbutanol and several 
drops--several mililliters of a solution of 1 g of potassium hydroxide (or 
0.7 g of sodium hydroxide) in 1.2 ml of water. The obtained mixture is 
stirred at 30.degree. C. for 3 hours. Then the mixture is partitioned 
between water and ether (or ethyl acetate). The upper phase is dried and 
solvent is removed by distillation from the upper phase. The residue is 
subjected to chromatography over alumina column eluting with 
cyclohexane:benzene (2:8 V/V) or other suitable solvent to give about 10 g 
of 16-dehydropregnenolone (about 41.6% on the basis of acidhydrolyzate). 
The obtained 16-dehydropregnenolone has the following physical properties: 
colorless plates, 
Rf: 0.41 (silica gel, chloroform:methanol=55:3 V/V) 
m.p.: 209.degree.-212.degree. c. 
angle of rotation: [.alpha.].sub.D.sup.22 =-36.degree. (c=2.0, chloroform) 
ultraviolet absorption: .lambda..sub.max =239 nm (log.epsilon.=3.91) 
When the syrupy substance is treated with boiling acetic acid in place of 
the aqueous alkali solution, 16-dehydropregnenolone acetate is obtained.