J . Am. Chem. SOC.1989, 1 1 1 , 647-654 mixture was quenched with saturated aqueous NH4CI, extracted with ether, washed with brine, dried (MgS04), and concentrated to give a colorless oily residue. To a stirred solution of the residue in CH2CI2(4 mL) was successively added Et,N (0.78 mL, 5.62 mmol) and CH,S02C1 (0.1 1 mL, 1.41 mmol) at -78 "C. The reaction mixture was stirred for 10 min at the same temperature, and then for 20 min at 0 O C . The reaction mixture was quenched with ice-water, extracted with ether, washed with brine, dried (MgS04), and concentrated. The residue was purified by silica gel column chromatography (hexane-ether, 1O:l) to give 21 (196 mg, 88%) in a ratio of 1(E):30(Z) as a colorless oil: for the Z-isomer 'H NMR (CDC1,) 6 0.06 (s, 12 H), 0.88, 0.92 (s and s, total 18 H), 1.10-1.88 (m, 4 H), 2.00-3.30 (m,7 H), 3.64 (d, J = 5.0 Hz, 1 H ) , 3 . 7 0 ( d , J = 3 . 5 H z , l H),3.92(ddd,J=6.5,8.5,8.5Hz,lH),6.02 (d, J = 2.0 Hz, 1 H), 6.30 (t, J = 7.5 Hz, 1 H); IR (neat) 2250, 1460 cm-'; MS (mlr),460 (M' - Me), 418 (M* - 'Bu,base peak), 286, 212, 186, 147, 117, 73; HRMS (M* - 'Bu) calcd for C2,HeN02Si2 418.2597, found 418.2568; for the E-isomer 'H NMR (CDCI,) 6 0.03,0.06 (s and s, total 12 H), 0.84, 0.90 (sands, total 18 H), 0.96 (t, J = 8.0 Hz, 3 H), 1.08-1.80 (m, 4 H), 1.96-2.90 (m, 7 H), 3.10 (m, 1 H), 3.62 (d, J = 5.5 Hz, 1 H), 3.63 (d, J = 4.0 Hz, 1 H), 3.91 (ddd, J = 7.0, 8.5, 8.5 Hz, 1 H), 6.02 (br s, 1 H), 6.10 (t, J = 7.8 Hz, 1 H); IR (neat) 2250, 1460 cm-I; MS ( m l z ) ,460 (M* - Me), 418 (M' - 'Bu,base peak), 286, 147, 73; HRMS (M' - 'Bu) calcd for C23H40N02Si2418.2597, found 41 8.2574. (1 s,5S ,6S ,7R ) -6-(( ( tert -Butyldimethylsilyl)oxy) methyl)-7-( ( tert -
647
butyldimethylsilyl)oxy)-(E)-3-(1-cyanopentylidene)bicyclo[3.3.0]octane (22a) and Its Z-Isomer (22b). A suspension of 10% Pd-C (5 mg, 10 mol %) in toluene (0.5 mL) was stirred at 23 O C for 0.5 h under 1 atm of H2 pressure. To a cooled (-40 "C) suspension was added 21 (22 mg, 0.05 mol, E : Z = 1:30) in toluene (1.5 mL), and the mixture was stirred for 4.5 h at -40 OC. The reaction mixture was filtered through silica gel and washed with ether. The combined filtrates were concentrated. The product was purified by silica gel column chromatography (hexaneether, 25:l) to give 22 (15 mg, 66%, 22a:22b = 10:l)"* as a colorless oil: for 22a, 'H NMR (CDCI,) 6 0.04, 0.05 (s and s, total 12 H), 0.87, 0.89 (s and s, total 18 H), 0.92 (t, J = 7.0 Hz, 3 H), 1.35 (m, 3 H), 1.52 (m, 3 H), 2.15 (m, 3 H), 2.23-2.65 (m, 5 H), 2.82 (m, 1 H), 3.55 (d, J = 6.0, 10.0 Hz, 1 H), 3.64 (d, J = 6.0, 10.0 Hz, 1 H), 3.91 (ddd, each J = 7.0 Hz, 1 H); IR (neat) 2250, 1480 cm-I; MS (mlz),477 (M'), 462 ( M c - Me), 420 (M'-'Bu), 288, 214, 189, 147, 133, 73; HRMS (M') calcd for C2,Hs1NO2Si2477.3458, found 477.3443; for 22b 'H NMR (CDC13) 6 0.04, 0.05 (s and s, 12 H), 0.87, 0.89 (s and s, 18 H), 0.92 (t, J = 7.5 Hz, 3 H), 1.33 (m, 3 H), 1.52 (m, 3 H), 2.15 (m, 3 H), 2.25-2.85 (m,6 H), 3.60 (d, J = 5.0 Hz, 2 H), 3.99 (ddd, each J = 7.0 Hz, 1 H); IR (neat) 2250, 1480 cm-'; MS ( m l z ) , 477 (M'), 462 (M' - Me), 420 (M'- 'Bu), 288, 214, 189, 147, 133, 73; HRMS (M') calcd for C2,Hs1NO2Si2477.3458, found 477.3476.
Acknowledgment. W e thank Yumiko Misu of our university for her help with t h e NMR studies.
Novel Sponge-Derived Amino Acids. 5. Structures, Stereochemistry, and Synthesis of Several New Heterocycles Madeline Adamczeski, Emilio QuifioQ,and Phillip Crews* Contribution from the Department of Chemistry and Institute for Marine Sciences, University of California, Santa Cruz, California 95064. Received March 9, 1988. Revised Manuscript Received August 2.5, 1988
Abstract: This paper reports the complete amino acid chemistry of an undescribed Jaspidae sponge, collected annually in the Benga lagoon of the Fiji Islands during the period from 1984 to 1987. Five different amino acid types are represented among its constituents and they include the bengamides (six compounds), isobengamide E, bengazoles (A and B), a diketopiperazine cyclo(~-trans-(4-hydroxyprolinyl)-~-phenylalanine), and N-acetyl-L-phenylalaninemethyl ester. The structures and stereochemical features of the bengamides were established by relying on analogies to bengamides A and B, along with insights gained by extensive spectroscopic and chemical degradation of isobengamide E and bengamide E. The chirality of the substituted c-caprolactam ring of the bengamides was established as ,lOSand 1 3 s by a combination of molecular mechanics calculations and hydrolysis of isobengamide E and bengamide E fragmentation products to obtain L-lysine hydrochloride. The relative stereochemistry of the 2(R*)-methoxy-3(R*),4(~*),5(R*)-trihydroxy-8-methylnon-6(E)-enoylside chain of the bengamides was based on analysis of 'H NMR Jvalues of cyclized products. The bengazole structures have been previously established, and the structures of the remaining two amino acids were verified by synthesis. Biogenetic pathways are suggested for each of the most novel amino acid types.
T h e study of nitrogen-containing heterocycles from Choristid sponges is a subject to which we and others are now devoting attention. T h e taxa from three families within this order, Jaspidae, Geodiidae, and Kallapididae, seem especially important because their multifarious natural products are almost always accompanied by exciting biological activity.* A few years ago we began a study of a n encrusting, globular, orange, undescribed Jaspidae sponge (1) Previous papers in this series are part 4, ref 17; part 3, ref 4; part 2, ref 3; and part 1, ref 2a. (2) Recent examples of novel cytotoxins are jasplakinolide [= jaspamide] from Jaspis johnstoni [Jaspidae]: (a) Crews, P.; Manes, L. V.; Boehler, M. Tetrahedron Lett. 1986, 27, 2797. (b) Zabriskie, T. M.; Klocke, J. A,; Ireland, C. M.; Marcus, A. H.; Molinski, T. F.; Faulkner, D. J.; Xu, C.; Clardy, J. J. Am. Chem. SOC.1986, 108, 3123. (c) Braekman, J. C.; Daloze, D.; Moussaiaux J. Nut. Prod. 1987, 50, 994. Calyculin A from Discodermia calyx [Kallapsidae]: (d) Kato, Y . ;Fusetani, N.; Matsunaga, S.; Hashimoto, K.; Fujiti, S.; Furuya, T. J. Am. Chem. SOC.1986, 108, 2780. The geodiamolides from Geodia sp. [Geodiidae]: (e) Pettit, G. R., Rideout, J. A,, Hasler, J. A. J. Nor. Prod. 1981, 33, 588. (f) Chan, W. R.; Tinto, W. F.; Manchand, P. S.;Todaro, L. J. J. Org. Chem. 1987, 52, 3091. The discodermins from Discodermia kiiemis [Gecdiidae]: (8) Matsunaga, s.;Fusetani, N.; Konosu, S. Tetrahedron Lett. 1985, 26, 855.
0002-7863/89/1511-0647$01.50/0
that was prominent in the coral reef communities throughout Fiji. Our early collections had extracts with potent anthelmintic activity that afforded atypical amino acid derivatives, bengamides A and B,3 as the only active constituents obtainable in large enough amounts t o permit structural characterization. Faint I3C NMR resonances between 40-60 and 150-180 ppm could be observed in anthelmintic-active solvent-partition fractions which intimated that other bioactive amino acids might be present. During the past 2 years we have obtained this sponge from many Fiji locations. By contrast, our pursuit of this sponge from locations outside of Fiji were unsuccessful as it could not be located in nearby south Pacific areas ranging from Tonga to Vanuatu to the Solomon Islands. It now seems appropriate to give a complete account of t h e remarkable chemistry of this sponge because it ranges from bengamides A (1) a n d B (2)3t o bengamides C-F (3-6), isobengamide E (7),bengazoles A (8) a n d B (9)4, di(3) Quiiiol, E.; Adamczeski, M.; Crews, P. J. Org. Chem. 1986,51,4494. (4) Adamczeski, M.; Quiioi, E.; Crews, P. J. Am. Chem. Soc. 1988, 110,
1598.
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Chemical Society
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ketopiperazine cyclo(~-tranr-(4-hydroxyprolinyl)-~-Phe) (lo), and N-acetyl-L-phenylalanine methyl ester (1 1). Two additional 'CH, 1
isobengamide E (7) A (1) and B (2) and to establish the structures of other new bengamide derivatives. The initial attributes of 7,C17H30N206 H = 359), and a 13C APT deduced by CIMS, EIMS (M' NMR spectrum, were established from spectroscopicand chemical properties along with comparisons to those of bengamides A (1) and B (2),. The unsaturation elements of 7 were similar to those of 1 and 2,as indicated by the very low field I3C N M R peaks, which included those from two carbonyls (174.1, s, 174.2, s) and the side-chain E double bond (140.2, d, 125.7, d; 5.71, dd, J = 15.4 and 6.5 Hz; 5.40, dd, J = 15.4 and 7.2 Hz). The 2-methoxy-3,4,5-trihydroxy-8-methyl-non-6(E)-enoyl group, also present in 1, was recognized in 7 by connectivities established in 'H-'H and 'H-l3C COSY NMR spectra, Furthermore, this Same COSY N M R data established that the t-caprolactam in 7 was also similar to that in bengamides A (1) and B (2),but the C H ( 0 ) of 1 at 6 = 70.9 (C-13) was shifted upfield in 7 (6 = 27, t), indicating that the amino acid present in isobengamide E was lysine and not 6-hydroxylysine. The two nitrogens and their associated hydrogens of 7 could be designated as N2H2by comparing the molecular formula to the C17H25count obtained from the APT spectrum and the presence of O H groups at C-5, (2-6, and (2-7. At this point there were two alternative structures, 5 and 7,that were consistent with the accumulated data. An absolute way to distinguish between these possibilities was provided by concurrent isolation of bengamide E (5),also of formula C17H30N206, and bengamide F ( 6 ) . The similar N M R properties of bengamide E (9, bengamide A (l),and bengamide B (2) were diagnostic of the identical environment of the NzH2atoms, as two secondary amides, in each of these compounds. The relevant 'H N M R shifts were at H-10 [(CDCl,) 1, 6 = 4.60; 2, 6 = 4.64; 5,6 = 4.53; (CD3OD) 2,6 = 4.681, and H-11 [(CDCl,) 1, 6 = 2.15, 1.75; 2,6 = 2.10, 1.57; 5, 6 = 1.99, 1.57; (CD,OD) 2,6 = 1.99, 1.551, and the average chemical shift difference at H-l1/11' was 0.45 f 0.08 ppm. The additional relatedness of bengamides E (5) and F (6)to the bengamides A (1)and B (2)was established by key IH-I3C COSY N M R resonances for both the ecaprolactam ring and the branched C-10 side chain. With bengamide A as a model, the especially diagnostic signals of C-lO/H-IO (6 51.5, d/4.60, m), C-ll/H-11 (28.9, t/2.15, m, 1.75, m), C-8/H-8 (81.3, d/3.80, m), and C-2/H-2 (30.9, d/2.29, m) could all be located in bengamides E and F as seen in Tables I and 11. The major difference between bengamides A and B, and E (5)and F (6)was the absence of the ester substituent at C-13 because in the latter two these carbon resonances were respectively 6 = 28.7 and 26.6. Furthermore, IH-I3C COSY ( J = 9 Hz) spectra (CDCI,) for 5 verified the attachment of the (2-10 side chain to the N-a, which is further attached to C-10 because a strong correlation was observed from H-a to C-9 (6 = 171.7), and correlations were also observed from H-11 and H-11' to C-16 (6 = 175.2). Strong lH--l3C COSY (J = 9 Hz, CDC1,) correlations were also observed to one of the carbonyls of 6,including from H- 11/-11', NMe-b, and H-14/14' to C-16 (6 = 172.3). Bengamides E and F behaved analogously to A and B when subjected to acetylation, and their respective acetates 22 and 23 had properties that were similar to those of acetates 20 and 21,which were obtained from bengamides A and B (Tables I and 11). Especially important was that the latter two bengamides were examined by IH-IH COSY N M R to verify the location of the branched side-chain OCH, substituent proposed at (2-8. Some key N M R features summarized above were different in isobengamide E (7)as follows: H-10 [(CD,OD) 6 = 4.131 and H-11 [(CD,OD) 6 = 1.72, 1.781, and the chemical shift difference at H- 11/ 11' was 0.06 ppm. Compound 7 was insoluble in CHCl,, whereas 1 and 5 exhibited identical solubility properties, as both
+
8 R = H (Bengazole A)
9 R = H(Bengazo1e B)
bengamides, 14 and 15,were also isolated but they are artifacts of the acid-catalyzed fragmentation from bengamides C and D.
10
11
The freshly collected sponge was immersed in C H 3 0 H and a viscous crude oil (14.07 g) was obtained. The isolation work was begun after executing the standard solvent-partitioning procedure of placing the crude extract in aqueous methanol and washing this successively with hexanes, CCl,, and CH2C12. The composition of the extract from the 1985 collection was rather simple, as bengamides A and B were the major components of both the CCl, and CH2Clz partition fractions. By contrast, the 1986 collection was extremely complex and an intricate approach was needed to successfully separate the components from the hexane, CCl,, and CH2C12 partition fractions of the crude extract as summarized in Chart I (see supplementary material). Highlights include the following: the hexane partition fraction (coded as A) provided lactone 13; the CC14 partition fraction (coded as B) provided 1,2,4-12,16,and 18;and the CH2C12partition fraction (coded as C) provided 3,5, 6,8-10, 17,and 18.
Rl H H H H H
H H H
Ac Ac Ac Ac Ac AC
The structure of isobengamide E (7)will be described first since the strategies to elucidate its structure and stereochemistry were utilized to complete the stereochemical assignments for bengamides
J. Am. Chem. Soc., Vol. 111 , No. 2, 1989 649
Novel Sponge-Derived Amino Acids were easily dissolvable in CHC13 and in MeOH. Also in contrast to the behavior of the latter was the behavior of isobengamide E under acetylation conditions, as this afforded N-acetylcyclolysine (27) accompanied by a 9:l mixture of the diacetylated lactone 18 and its dehydro analogue, 19. The facile acyl cleavage assisted n
Scheme I bengarnide E I
5
1
0
isobengamideE 22
z
by the &hydroxy group, resulting in intramolecular esterification5 for 7 and not 5 under acetylation conditions (or with catalytic toluenesulfonic acid, TSA), is consistent with the better leaving group ability expected for the imide type nitrogen of the former as compared to that of the amide type nitrogen of the latter. Consequently, isobengamide E was assigned as gross structure 7 with primary amine and tertiary imide type nitrogens. The results of several additional chemical transformations are summarized in Scheme I. Analysis of the derivatives which we obtained further supported the proposed structure of 7 and enabled the assignment of the absolute stereochemistry of the lysine subunit as well as the relative stereochemistry of the C-10 side chain. Treatment of 7 with 2,2-dimethoxypropane (DMP) and catalytic TSA in acetone afforded cyclolysine (26), along with a 4:l mixture 6
-
24
1
13 R = H 19 R = A c
12 R = H 18 R = A c
v
AclO
f
TSA
-31
DMP
H+
0
II H+
L-lysine
25 29
Chart I1
PHI
0 HO H
o3 q :4
24 R = H 25 R = A c
+R
no
12
i H-H (J)'
\
1
R2
26 R , = H R 2 = H 27 R, = AC R, = H 28 R, = A c R2 = OAC
A I
I
H3C
trans
MeOD/CD3CN
2-3
4.5
4.2
4.2
4.5-5.7
8.5-8.9
3-4
3.0
2.7
2.7
2.8-3.0
8.2-8.6 0 - 0.1
15
CH,
cis
CDCI, MeOD
H-H(J)
uRef. 6
of the dioxolane acid 30 and the bicyclic lactone 32 (Chart 111). The position of the dioxolane ring in 30 was conclusively deduced by its further transformation to the corresponding acetate 31, in which proton connectivities were established by 'H-IH COSY N M R . The fragmentation product 27, obtained from 7 during acetylation, was subjected to acidic hydrolysis, yielding lysine as its cationic salt, whose rotation ([.]"D = +15.7', c = 7.1 x D 2 0 ) was virtually identical with that of authentic L-lysine hydrochloride ([.]*OD = +16.0°, c = 1.0 X lo-', D20). This established the absolute stereochemistry of C-10 as S in 7. Lactones 12 (Chart 11) and 13 (Scheme I) were isolated as constituents of the crude oil, and their relationship to lactones 18 and 19, obtained from the degradation of 7, was demonstrated as follows. Conversion of 12 to 18, 32, or 13 was accomplished by using conditions which were respectively acetylation, reaction with 2,2-dimethoxypropane, or reaction with TSA. Analogously,
13 was smoothly acetylated to 19. The relative stereochemistry of the four chiral centers of the C-10 side chain of isobengamide E was assigned by analysis of 'H 3Jvalues of compounds related to it as shown in Scheme I, including dioxolane 30,dioxane lactone 32, and the lactone 12. Recently, we employed the characteristic J values at C-4/5 in a 1,3-dioxolane of 8.35-8.45 Hz for trans and 4.72-5.85 Hz for cis substitution to establish the stereochemistry of highly substituted d i o ~ o l a n e s .The ~ dioxolane ring of 30 exhibited J5+= 8.7 Hz, which unambiguously indicated a trans relationship between these protons and, thus, a threo relationship between H-5 and H-6 in isobengamide E. The relative stereochemistry at the remaining three C's (6-8) could be decided from the analysis of the two lactones. A wealth of NMR J values are available from Serianni's extensive conformational analysis of aldono- 1,4-la~tones,~ and Chart I1 summarizes the variation of the J values as the proton stereochemistry changes at each ring position for nine compounds of structure i (Serianni's numbering). Also listed in Chart I1 are 'H NMR Jvalues, measured in three different solvents, for lactone
(5) Helmchen, G.; Nill, G.; Flockerzi, D.; Youssef, M. S . K. Angew. Chem., Int. Ed. Engl. 1979, 18, 63.
(6) Angelotti, T.; Krisko, M.; OConnor, T.; Serianni, A. S. J . Am. Chem. SOC.1987, 109, 4464.
30 R = H 31 R = A c
650 J . Am. Chem. SOC..Vol. 111, No. 2, 1989
Adamczeski et ai.
Table I. 'H NMR Data of Some of the Compounds Discussed (CDCI,, 300 MHz) H no. 1 2 3 4 5 6 7 8 9 10 11
1 mult d
6 0.99 2.29 5.78 5.44 4.21 3.60 3.80 3.80 4.60 1.75 2.15 1.95 2.15 4.60
12 13
6.9
m dd dd t brs m m
6.5, 15.5 7.3, 15.5 6.0
m
m m m
3.32
brm
15 16 17 18 19 20-27 28 29 30 N*
0.99
d
6.9
2.29 1.59 1.4-1.2 1.4-1.2 1.4-1.2 0.87 7.97 8.10 6.28 4.27 3.52
t m brs brs brs t d d t brs
7.5
OH OMe NMe
0.95 2.26 5.72 5.40 4.17 3.55 3.76 3.76 4.64 1.57 2.10 1.95 2.10 4.55
m
14
Nb
s
J , Hz
(20 H) 6.5 6.3 (>90%) 6.3 (95%) 6.6 (go%) 6.6 (
