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A rearranged abietane diterpenoid from the root of Teucrium fruticans
0031-9422/90 $3.00+0.00 $? 1990 PergamonPressplc
Phytochemistry, Vol. 29, No. 8, pp. 271c-2712, 1990. Printedin Great Britain.
A REARRANGED
MAURIZIO
BRUNO, MARiA C.
Dipartimento di Chimica
ABIETANE DITERPENOID FROM*THE TEUCRIUM FRUTICANS DE LA TORRE,*
Organica,
GIUSEPPE SAVONA, FRANCO Prozzr
Universita di Palermo, Archirafi 20, 90123 Palermo, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
ROOT OF
and BENJAMiN RODRiGUEZ*
Italy; *Institute
de Quimica
OrgBnica,
(Receioed 18 Janunry 1990) Key Word Index---Teucriumfruticans;
Labiatae;
root; 17(15-+ 16),18(4+3)-diahro-abietane
derivative:
teuvincenone
E.
Abstract-From the root of Teucrium fiuticans a new rearranged abietane diterpenoid, teuvincenone E, has been isolated. Its structure [(16S)-12,16-epoxy-11,14-dihydroxy-17(15-,16),18(4~3)-diabro-abieta-3,5,8,1 1,13-pentaene2,7-dione] was established by spectroscopic means and by comparison with closely related compounds.
INTRODUCTION
RESULTS AND DISCUSSION
Recently we have focussed our attention on the diterpenoid constituents of the root of Teucrium species [l]. Continuing this study, we have now investigated the root of T. fruticans, from which a new rearranged abietane diterpenoid has been isolated. We propose the name teuvincenone E for this compound, whose structure (1) has been established on the basis of spectroscopic evidence and by comparison with closely related compounds such as (16S)- and (16R)-plectrinone A (2 and 3, respectively) [2, 31, and teuvincenone A (4) [l].
Combustion analysis and low-resolution mass spectrometry indicated the molecular formula C,,H,,05 for teuvincenone E (I). Its UV spectrum obtained in neutral medium (methanol, see Table 1) was identical with those reported for (16S)- and (16R)-plectrinone A (2 and 3, respectively) [2,3], thus establishing that compounds l-3 possess the same chromophore. This conclusion was also supported by the UV spectra of teuvincenone E obtained after addition of base, aluminium chloride and aluminium chloride plus hydrochloric acid (Table I), which
2
(165)
3 (16R) -
O
4
‘.
H
Ii0 /
0
A’ 0
\
19
O...‘”
\\
116 0 + :
4
2710
Short Reports
2711
Table 1. UV spectra of compound 1 [n,,, nm (log
E)]
MeOH
+ NaOMe
+ AICl,
+ AlCI,-HCI
+ NaOAc-H,BO,
254(sh) (3.92)
252 (4.10) 299 (4.19) 354(sh) (3.71)
269 (4.00) 298(sh) (4.13) 309 (4.16) 335(sh) (3.87) 388 (3.74) 498 (3.52)
268 (4.02) 299(sh) (4.12) 308 (4.15) 335(sh) (3.86) 386 (3.71) 498 (3.52)
254(sh) (3.97) 298 (4.25) 370(sh) (3.60) -430(sh) (3.53)
298 (4.24) 370(sh) (3.57) -430(sh) (3.52)
showed characteristic band shifts of a cross-conjugated chromophore constituted by an a,/I,y&diunsaturated ketone moiety and a 2,5-dihydroxy-3,6-dialkyl-4alkoxyphenylketone grouping [l, 4, 51. The ‘H and i3CNMR spectra of teuvincenone E (1) were almost identical with those of (16S)-plectrinone A (2, Tables 2 and 3). In fact, the only differences were consistent with the presence in compound 1 of an a-methyl dihydrofuran (ring D, see formula l), condensed with the fully substituted aromatic ring, instead of the 2-hydroxyn-propyl side-chain and the C-12 phenolic group of compound 2 [l, 31. The heteroatom of the dihydrofuran fragment of teuvincenone E must be attached to the C-12 position, because no shifts were observed in the UV spectrum of this compound (1) when it was measured in the presence of boric acid plus sodium acetate (see Table l), thus excluding the existence of an ortho-diphenol group [ 1,4] in the molecule of this new diterpenoid. The existence in compound 1 of a phenolic proton strongly chelated (singlet at 6 13.34, Table 2), which was undoubtedly assigned to the C-14 phenol function [l-3], also supported this conclusion and ruled out an alternative structure with the dihydrofuran oxygen atom attached to the C-14 position. The stereochemistry at the C-16 asymmetric centre of teuvincenone E (1) must be the same that in teuvincenone A (4, aH, /IMe) [l], as was revealed by the identical chemical shifts and coupling values of the H-15a, H-15/& H-16a and Me-17 protons (Table 2). The almost identical chemical shifts of the C-15, C-16 and C-17 carbons in both compounds (1 and 4, Table 3) also supported this point. The absolute configuration of teuvincenone E (1) was not ascertained. However, on biogenetic grounds, it is reasonable to assume that 1 possesses a normal abietane absolute stereochemistry such as teuvincenones A (4), B, C (5) and D, all of which occur in the root of Teucrium polium subsp. vincentinum. From a biogenetic point of view, it is interesting that all the diterpenoids isolated so far from the root of Teucrium species [teuvincenones A (4), B, C (5), D [l] and E (l)] possessa(16S)-12,16-epoxy-11,14-dihydroxy-17(15~16)abeo-abieta-8,11,13-trien-7-one structural moiety. Moreover, the isolation of teuvincenone E (1) from the root of T.fiuticans supports a previous hypothesis [l] according to which the 17(15+16)-abeo-3a,l8cycloabietane derivatives, such as teuvincenones C (5) and D Cl], may be considered as biogenetic intermediates between the 17(15+ 16)~abeo-abietanes, like teuvincenones A (4) and B Cl], and the 17(15+16),18(4+3)-diabeo-abietane derivatives, such as teuvincenone E (1) and (16S)- and (16R)plectrinone A (2 and 3, respectively) [2, 31.
Table 2. ‘H NMR spectral parameters of compounds 1 and 2 and related data of compound 4 (CDCI,, TMS as int. standard) H
1*
2t
1Or
2.43 dq
1B
4.17 d
2.43 dq 4.19 d 6.53 s 3.07 m 2.87 m 4.33 m 1.33 d 1.99 q 2.21 q 1.63 d
6 15a 15P
16a Me-17 Me-18 Me-19 Me-20 OH-l 1s OH-1411
J U-W la,lB la, Me-20 15a,15B 15aJ6a 15/I,16a 16a, Me-17 Me-18, Me-19
6.53 s 3.42 dd 2.90 dd 5.17 ddq 1.54d 2.01 q 2.22 q 1.63 d 5.11 br s 13.34 s 16.7 0.6 15.4 8.9 7.3 6.3 1.1
ll
13.58 s 16.7 0.7 14.9 7.2 2.3 6.2 1.0
4$
3.43 dd 2.91 dd 5.18 ddq 1.55 d
4.91 s 12.44 s
15.5 9.0 7.3 6.3
*Spectral parameters were obtained by first order approximation. All these assignments have been confirmed by double resonance experiments and the ‘H-‘H 2D COSY spectrum. tTaken from ref. [3]. STaken from ref. [l]. §Rapidly interchangeable with D,O. llSlowly interchangeable with D,O. BNot reported [3].
EXPERIMENTAL
Mp: uncorr. For general details on methods, see ref. [l]. Plant materials were collected in May 1988, near Palermo, Sicily (Italy), and voucher specimens were deposited in the Herbarium of the Botanic Garden of Palerrno, Italy. Extraction and isolation ofteuuincenone E (1). Dried and finely powdered T. fruticans L. roots (1.2 kg) were extracted twice with Me,CO (4 1) at room temp. for a week. The extract (20 g) was chromatographed on a silica gel (Merck, No. 7734, deactivated with 15% H,O, 300 g) column eluted with n-hexane and nhexane-EtOAc mixtures. From the fraction eluted with nhexane_EtOAc (2: l), 18 mg of impure teuvincenone E (1) were isolated. Rechromatography (silica gel, n-hexane_EtOAc 2: 1 as eluent) and crystallization from MeOH gave pure teuvincenone
Short Reports
2712 Table
3. 13C NMR chemical shifts of diterpenoids 2 and 4 (CDCI,, TMS as int. standard)
C
1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
45.37 197.30 131.02 146.15 160.58 123.92 188.86 108.76 134.18 42.60 136.17 154.58 111.83 154.72 34.33 83.44 21.96 11.97 17.42 24.89
2* t: s s s s d s s s s s sa s sa
t d q q q q
E (1, 8 mg, red needles): mp 237-238”; [a]A’+80.2” (CHCI,; cO.l77).IRv~~;cml. 3140 (OH), 3500-2500 (br, chelated OH at C-14), 1670 (ketone at C-2), 1648 (chelated aryl ketone at C-7), 1630, 1600, 1570 (aromatic and olefinic) 2980, 2940, 1475, 1455, 1400, 1325, 1225, 1025, 1015, 980, 890, 820. UV: see Table I. ‘H NMR (300 MHz, CDCl,): see Table 2; 13C NMR (75.4 MHz, CDCl,): see Table 3; EIMS (70 eV, direct inlet) m/z (rel. int.): 340 [M]+ (33), 325(100),323(16). 322(7),310(5), 307(15),297(15), 279 (lo), 255 (7). 215 (lo), 129 (7), 115 (7), 43 (6). (Found: C, 70.43; H, 6.06. C,,H,,O, requires: C, 70.57; H. 5.92%.)
1,
4t
45.1 t 196.5 s 131.1 s 146.1 s 161.2 s 123.8 d 189.7 s 107.4 s 136.2 s 42.5 s 136.5 s 152.0 s 112.0 s 157.0 s 31.4 t 69.6 d 22.5 q 11.6q 17.1 q 24.5 q
21.05 t 33.08 t 214.50 s 48.68 s 139.99 s 140.03 s 182.92 s 107.14 s 135.20 s 40.60 s 131.20 s 153.80s 111.50 s 154.83 s 34.35 t 83.54 d 21.98 q 21.08 q 20.11 q 24.36 q
Acknowledgements-This work was subsidized by the Spanish ‘Direccibn General de Investigacibn Cientifica y TCcnica’ (Grant No. PB87-0418), ‘Scientific Research Funds’ from the Italian Ministry of Education, and “Programa Conjunto CSIC-CNR No. 3.3”. One of us (M.C. de la T.) thanks the CSIC for a fellowship.
REFERENCES 1. Carreiras,
2. 3. 4.
*Taken from ref. [3]. tTaken from ref. [l]. SDEPT multiplicity. “These assignments may be interchanged.
5.
M. C., Rodriguez. B., de la Torre, M. C., Perales, A., Torres, M. R., Savona. G. and Piozzi, F. (1990) Tetrahedron 46, 847. Alder, A. C., Riiedi, P., Prewo, R.. Bieri, J. H. and Eugster. C. H. (1986) He/u. Chim. Acta 69, 1395. Riiedi, P. (1986) Helo. Chim. Acta 69, 972. Mabry, T. J., Markham, K. R. and Thomas, M. B. (1970) The Systematic Identification c$ Flaconoids Chap. IV. Springer, New York. Hueso-Rodriguez, J. A., Jimeno, M. L., Rodriguez, B., Savona, G. and Bruno, M. (1983) Phyrochemistry 22, 2005.
0031 9422/90%3.00+0.00 Pergamon Press plc
Phytochemistry,Vol. 29, No. 8, pp. 2712-2715,1990. Printed in Great Britain.
ANTHONY
G. AVENT, JAMES R. HANSON* and
BRAS H. DE OLIVEIRA
The School of Molecular Sciences, University of Sussex, Brighton, BNl 9QJ. U.K. (Receioed
Key Word Index-Steuia
rebaudiana;
Compositae;
15 December stevioside;
1989)
diterpenoid;
glycoside;
Abstract-The minor products from the acid-catalysed hydrolysis of the diterpenoid identified and the location of the deuterium has been established when the hydrolysis deuterium bromide.
INTRODUCTION The diterpenoid glycoside, stevioside (1) which is obtained from Steuia rebaudiana [l], is produced commercially in the Far East and South America as a sugar substitute. The bio-transformation of the aglycone steviol (2) and its relatives has been of interest in the light of its similarity to gibberellin biosynthetic intermediates [2-~51. Enzymatic hydrolysis of stevioside by the gastric juices of
hydrolysis.
aglycones.
glycoside, stevioside have been is carried out in the presence of
the snail, Helix porn&a, [6], pectinase [7] or hesperidinase [S] affords the aglycone, steviol(2). On the other hand hydrolysis with mineral acid affords [6, 9-111 the Wagner-Meerwein rearrangement product, isosteviol(3). A chemical method of obtaining steviol from stevioside involves oxidation of the sugars with periodate and hydrolysis with base [12]. In this paper we report a more detailed study of the acid-catalysed hydrolysis.
Phytochemistry, Vol. 29, No. 8, pp. 271c-2712, 1990. Printedin Great Britain.
A REARRANGED
MAURIZIO
BRUNO, MARiA C.
Dipartimento di Chimica
ABIETANE DITERPENOID FROM*THE TEUCRIUM FRUTICANS DE LA TORRE,*
Organica,
GIUSEPPE SAVONA, FRANCO Prozzr
Universita di Palermo, Archirafi 20, 90123 Palermo, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
ROOT OF
and BENJAMiN RODRiGUEZ*
Italy; *Institute
de Quimica
OrgBnica,
(Receioed 18 Janunry 1990) Key Word Index---Teucriumfruticans;
Labiatae;
root; 17(15-+ 16),18(4+3)-diahro-abietane
derivative:
teuvincenone
E.
Abstract-From the root of Teucrium fiuticans a new rearranged abietane diterpenoid, teuvincenone E, has been isolated. Its structure [(16S)-12,16-epoxy-11,14-dihydroxy-17(15-,16),18(4~3)-diabro-abieta-3,5,8,1 1,13-pentaene2,7-dione] was established by spectroscopic means and by comparison with closely related compounds.
INTRODUCTION
RESULTS AND DISCUSSION
Recently we have focussed our attention on the diterpenoid constituents of the root of Teucrium species [l]. Continuing this study, we have now investigated the root of T. fruticans, from which a new rearranged abietane diterpenoid has been isolated. We propose the name teuvincenone E for this compound, whose structure (1) has been established on the basis of spectroscopic evidence and by comparison with closely related compounds such as (16S)- and (16R)-plectrinone A (2 and 3, respectively) [2, 31, and teuvincenone A (4) [l].
Combustion analysis and low-resolution mass spectrometry indicated the molecular formula C,,H,,05 for teuvincenone E (I). Its UV spectrum obtained in neutral medium (methanol, see Table 1) was identical with those reported for (16S)- and (16R)-plectrinone A (2 and 3, respectively) [2,3], thus establishing that compounds l-3 possess the same chromophore. This conclusion was also supported by the UV spectra of teuvincenone E obtained after addition of base, aluminium chloride and aluminium chloride plus hydrochloric acid (Table I), which
2
(165)
3 (16R) -
O
4
‘.
H
Ii0 /
0
A’ 0
\
19
O...‘”
\\
116 0 + :
4
2710
Short Reports
2711
Table 1. UV spectra of compound 1 [n,,, nm (log
E)]
MeOH
+ NaOMe
+ AICl,
+ AlCI,-HCI
+ NaOAc-H,BO,
254(sh) (3.92)
252 (4.10) 299 (4.19) 354(sh) (3.71)
269 (4.00) 298(sh) (4.13) 309 (4.16) 335(sh) (3.87) 388 (3.74) 498 (3.52)
268 (4.02) 299(sh) (4.12) 308 (4.15) 335(sh) (3.86) 386 (3.71) 498 (3.52)
254(sh) (3.97) 298 (4.25) 370(sh) (3.60) -430(sh) (3.53)
298 (4.24) 370(sh) (3.57) -430(sh) (3.52)
showed characteristic band shifts of a cross-conjugated chromophore constituted by an a,/I,y&diunsaturated ketone moiety and a 2,5-dihydroxy-3,6-dialkyl-4alkoxyphenylketone grouping [l, 4, 51. The ‘H and i3CNMR spectra of teuvincenone E (1) were almost identical with those of (16S)-plectrinone A (2, Tables 2 and 3). In fact, the only differences were consistent with the presence in compound 1 of an a-methyl dihydrofuran (ring D, see formula l), condensed with the fully substituted aromatic ring, instead of the 2-hydroxyn-propyl side-chain and the C-12 phenolic group of compound 2 [l, 31. The heteroatom of the dihydrofuran fragment of teuvincenone E must be attached to the C-12 position, because no shifts were observed in the UV spectrum of this compound (1) when it was measured in the presence of boric acid plus sodium acetate (see Table l), thus excluding the existence of an ortho-diphenol group [ 1,4] in the molecule of this new diterpenoid. The existence in compound 1 of a phenolic proton strongly chelated (singlet at 6 13.34, Table 2), which was undoubtedly assigned to the C-14 phenol function [l-3], also supported this conclusion and ruled out an alternative structure with the dihydrofuran oxygen atom attached to the C-14 position. The stereochemistry at the C-16 asymmetric centre of teuvincenone E (1) must be the same that in teuvincenone A (4, aH, /IMe) [l], as was revealed by the identical chemical shifts and coupling values of the H-15a, H-15/& H-16a and Me-17 protons (Table 2). The almost identical chemical shifts of the C-15, C-16 and C-17 carbons in both compounds (1 and 4, Table 3) also supported this point. The absolute configuration of teuvincenone E (1) was not ascertained. However, on biogenetic grounds, it is reasonable to assume that 1 possesses a normal abietane absolute stereochemistry such as teuvincenones A (4), B, C (5) and D, all of which occur in the root of Teucrium polium subsp. vincentinum. From a biogenetic point of view, it is interesting that all the diterpenoids isolated so far from the root of Teucrium species [teuvincenones A (4), B, C (5), D [l] and E (l)] possessa(16S)-12,16-epoxy-11,14-dihydroxy-17(15~16)abeo-abieta-8,11,13-trien-7-one structural moiety. Moreover, the isolation of teuvincenone E (1) from the root of T.fiuticans supports a previous hypothesis [l] according to which the 17(15+16)-abeo-3a,l8cycloabietane derivatives, such as teuvincenones C (5) and D Cl], may be considered as biogenetic intermediates between the 17(15+ 16)~abeo-abietanes, like teuvincenones A (4) and B Cl], and the 17(15+16),18(4+3)-diabeo-abietane derivatives, such as teuvincenone E (1) and (16S)- and (16R)plectrinone A (2 and 3, respectively) [2, 31.
Table 2. ‘H NMR spectral parameters of compounds 1 and 2 and related data of compound 4 (CDCI,, TMS as int. standard) H
1*
2t
1Or
2.43 dq
1B
4.17 d
2.43 dq 4.19 d 6.53 s 3.07 m 2.87 m 4.33 m 1.33 d 1.99 q 2.21 q 1.63 d
6 15a 15P
16a Me-17 Me-18 Me-19 Me-20 OH-l 1s OH-1411
J U-W la,lB la, Me-20 15a,15B 15aJ6a 15/I,16a 16a, Me-17 Me-18, Me-19
6.53 s 3.42 dd 2.90 dd 5.17 ddq 1.54d 2.01 q 2.22 q 1.63 d 5.11 br s 13.34 s 16.7 0.6 15.4 8.9 7.3 6.3 1.1
ll
13.58 s 16.7 0.7 14.9 7.2 2.3 6.2 1.0
4$
3.43 dd 2.91 dd 5.18 ddq 1.55 d
4.91 s 12.44 s
15.5 9.0 7.3 6.3
*Spectral parameters were obtained by first order approximation. All these assignments have been confirmed by double resonance experiments and the ‘H-‘H 2D COSY spectrum. tTaken from ref. [3]. STaken from ref. [l]. §Rapidly interchangeable with D,O. llSlowly interchangeable with D,O. BNot reported [3].
EXPERIMENTAL
Mp: uncorr. For general details on methods, see ref. [l]. Plant materials were collected in May 1988, near Palermo, Sicily (Italy), and voucher specimens were deposited in the Herbarium of the Botanic Garden of Palerrno, Italy. Extraction and isolation ofteuuincenone E (1). Dried and finely powdered T. fruticans L. roots (1.2 kg) were extracted twice with Me,CO (4 1) at room temp. for a week. The extract (20 g) was chromatographed on a silica gel (Merck, No. 7734, deactivated with 15% H,O, 300 g) column eluted with n-hexane and nhexane-EtOAc mixtures. From the fraction eluted with nhexane_EtOAc (2: l), 18 mg of impure teuvincenone E (1) were isolated. Rechromatography (silica gel, n-hexane_EtOAc 2: 1 as eluent) and crystallization from MeOH gave pure teuvincenone
Short Reports
2712 Table
3. 13C NMR chemical shifts of diterpenoids 2 and 4 (CDCI,, TMS as int. standard)
C
1
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
45.37 197.30 131.02 146.15 160.58 123.92 188.86 108.76 134.18 42.60 136.17 154.58 111.83 154.72 34.33 83.44 21.96 11.97 17.42 24.89
2* t: s s s s d s s s s s sa s sa
t d q q q q
E (1, 8 mg, red needles): mp 237-238”; [a]A’+80.2” (CHCI,; cO.l77).IRv~~;cml. 3140 (OH), 3500-2500 (br, chelated OH at C-14), 1670 (ketone at C-2), 1648 (chelated aryl ketone at C-7), 1630, 1600, 1570 (aromatic and olefinic) 2980, 2940, 1475, 1455, 1400, 1325, 1225, 1025, 1015, 980, 890, 820. UV: see Table I. ‘H NMR (300 MHz, CDCl,): see Table 2; 13C NMR (75.4 MHz, CDCl,): see Table 3; EIMS (70 eV, direct inlet) m/z (rel. int.): 340 [M]+ (33), 325(100),323(16). 322(7),310(5), 307(15),297(15), 279 (lo), 255 (7). 215 (lo), 129 (7), 115 (7), 43 (6). (Found: C, 70.43; H, 6.06. C,,H,,O, requires: C, 70.57; H. 5.92%.)
1,
4t
45.1 t 196.5 s 131.1 s 146.1 s 161.2 s 123.8 d 189.7 s 107.4 s 136.2 s 42.5 s 136.5 s 152.0 s 112.0 s 157.0 s 31.4 t 69.6 d 22.5 q 11.6q 17.1 q 24.5 q
21.05 t 33.08 t 214.50 s 48.68 s 139.99 s 140.03 s 182.92 s 107.14 s 135.20 s 40.60 s 131.20 s 153.80s 111.50 s 154.83 s 34.35 t 83.54 d 21.98 q 21.08 q 20.11 q 24.36 q
Acknowledgements-This work was subsidized by the Spanish ‘Direccibn General de Investigacibn Cientifica y TCcnica’ (Grant No. PB87-0418), ‘Scientific Research Funds’ from the Italian Ministry of Education, and “Programa Conjunto CSIC-CNR No. 3.3”. One of us (M.C. de la T.) thanks the CSIC for a fellowship.
REFERENCES 1. Carreiras,
2. 3. 4.
*Taken from ref. [3]. tTaken from ref. [l]. SDEPT multiplicity. “These assignments may be interchanged.
5.
M. C., Rodriguez. B., de la Torre, M. C., Perales, A., Torres, M. R., Savona. G. and Piozzi, F. (1990) Tetrahedron 46, 847. Alder, A. C., Riiedi, P., Prewo, R.. Bieri, J. H. and Eugster. C. H. (1986) He/u. Chim. Acta 69, 1395. Riiedi, P. (1986) Helo. Chim. Acta 69, 972. Mabry, T. J., Markham, K. R. and Thomas, M. B. (1970) The Systematic Identification c$ Flaconoids Chap. IV. Springer, New York. Hueso-Rodriguez, J. A., Jimeno, M. L., Rodriguez, B., Savona, G. and Bruno, M. (1983) Phyrochemistry 22, 2005.
0031 9422/90%3.00+0.00 Pergamon Press plc
Phytochemistry,Vol. 29, No. 8, pp. 2712-2715,1990. Printed in Great Britain.
ANTHONY
G. AVENT, JAMES R. HANSON* and
BRAS H. DE OLIVEIRA
The School of Molecular Sciences, University of Sussex, Brighton, BNl 9QJ. U.K. (Receioed
Key Word Index-Steuia
rebaudiana;
Compositae;
15 December stevioside;
1989)
diterpenoid;
glycoside;
Abstract-The minor products from the acid-catalysed hydrolysis of the diterpenoid identified and the location of the deuterium has been established when the hydrolysis deuterium bromide.
INTRODUCTION The diterpenoid glycoside, stevioside (1) which is obtained from Steuia rebaudiana [l], is produced commercially in the Far East and South America as a sugar substitute. The bio-transformation of the aglycone steviol (2) and its relatives has been of interest in the light of its similarity to gibberellin biosynthetic intermediates [2-~51. Enzymatic hydrolysis of stevioside by the gastric juices of
hydrolysis.
aglycones.
glycoside, stevioside have been is carried out in the presence of
the snail, Helix porn&a, [6], pectinase [7] or hesperidinase [S] affords the aglycone, steviol(2). On the other hand hydrolysis with mineral acid affords [6, 9-111 the Wagner-Meerwein rearrangement product, isosteviol(3). A chemical method of obtaining steviol from stevioside involves oxidation of the sugars with periodate and hydrolysis with base [12]. In this paper we report a more detailed study of the acid-catalysed hydrolysis.