SYNTHESIS OF AMINONUCLEOSIDES
Nov. 20, 1955
5905
fonyl chloride. The solution was heated in a bath a t 51" vacuo. The residue was heated on the steam-bath with 4 in a flask protected by a drying tube for 22 hr. The solu- cc. of pyridine and 4 cc. of acetic anhydride for 1 hr. The tion was diluted with 55 cc. of water and extracted with mixture, dilute with 25 cc. of water, was extracted with chloroform (3 X 20 cc.). The combined extracts, washed chloroform (4 X 15 cc.). The combined extracts were dried with magnesium sulfate and evaporated to dryness with aqueous sodium bicarbonate and dried with magnesium sulfate, were evaporated to dryness in vacuo. The residue in ZJUCUOleaving280 mg. (717,) of product as a glass. In a pilot run the yield was 68% (80 mg.). This comwas dissolved in 10 cc. of toluene and the evaporation repeated to remove pyridine; yield 1.09 g. (87%) of a glass pound had: : :A 3.02 p (NH), 5.71, 8.17 p (0-acetate), 5.98, which contained some triphenylcarbinol. 6.52 p (amide), 6.25 p (C=N) and no sulfonate absorption 2-Methylmercapto-6-dimethylamino-9-( 2 '-0-mesyl-3 '- a t 8.33 p . The compound is probably contaminated with acetamido-3'-deoxy-p-~-arabinofranosyl)-purine(XVII).some triacetate of XI. A mixture of 790 mg. of XIV and 15.8 cc. of 807, acetic acid Anal. Calcd. for C,sH&eOeS: C, 48.9; H, 5.62; S , was heated for 22 minutes on the steam-bath, solution being 18.0. Found: C,48.6; H, 5.79; N, 17.7. complete in 2 minutes. The solution was diluted with 100 6-Dimethylamino-9-(2 ',5 '-di-O-acetyl-J '-acetamido-3 'cc. of hot water and extracted with two 100-cc. portions of hot heptane to remove triphenylcarbinol. The aqueous deoxy-p-D-ribofuranosy1)-purine (XV).-To a solution of solution was filtered from a small amount of solid, then evap- 280 mg. of XVI in 50 cc. of methyl Cellosolve was added orated to dryness in vacuo leaving 390 mg. (75%) of a glass about 1.5 g. of desulfurizing Raney nickel.8 The mixture with: : :A 3.0 p (OH, NH), 6.00, 6.50 p (amide), 6.23 p was stirred on the steam-bath for 1 hour, then filtered hot through Celite using hot methyl Cellosolve for washing. (C=N), 8.33 p (sulfonate) and no appreciable absorption Evaporation to dryness in vacuo left 135 mg. of a glass. at 14.3 p (monosubstituted phenyl from the triphenylCrJistallization from ethyl acetate gave 64 mg. (24%) of methyl group). The compound was not pure. white crystals, m.p. 182-183'. Recrystallization from 2-Methylmercapto-6-dimethylamino-9-(2 ' , 5 '-di-0-acetylThe ethyl acetate afforded white crystals, m.p. 188-189'. 3'-acetamido-3'-deoxy-p-~-ribofuranosyl)-purine(XVI).-A product was identical with authentic XV1 as shown by mixture of 388 mg. of XVII, 282 mg. of anhydrous sodium mixed m.p. and infrared spectra. acetate and 4 cc. of methyl Cellosolve containing 55; water PEARL RIVER,SEW YORK WVBSrefluxed for 23 hours, then evaporated to dryness in
[COSTRIRU? ION
Puromycin.
FROM TKE
MEDICISALCHEMICALRESEARCH SECTIOH, LEDERLE LABORATORIES, RESEARCH DIVISION, AMERICANCYANAMID COMPANY]
Synthetic Studies. XIV. Use of the N-Phthalyl Blocking Group for Synthesis of Aminonucleosides BY B. R. BAKER,J. P.
JOSEPH AND
R. E. SCHAUB
RECEIVED JUNE 9, 1955 The preparation of 2,5-di-O-benzoyl-3-phthalimido-3-deoxy-~-~-ribofuranosyl chloride (Vb) by proper degradation of the antibiotic puromycin and by total synthesis from D-xylose is described. The advantage and disadvantages of this phthalimido sugar compared to the corresponding acetamido sugar for the synthesis of biologically active aminonucleosides are shown.
To avoid these difficulties it would be necessary One of the key steps in the total synthesis of puromycin' is the conversion of l-O-acetyl-2,5-di-O- to prepare the chloroacyl aminosugar by a method benzoyl-3-acetamido-3-deoxy-~-ribofuranose to 2,5- not involving titanium tetrachloride. The usual method for preparation of chloroacyl furanosides, di - 0 -benzoyl -3-acetamido-3-deoxy-~-ribofuranosy~ chloride-titanium chloride complex, which is con- namely, hydrogen chloride in ether, failed with the densed, without isolation, with chloromercuri-2- N-acetyl blocking group due to the weakly basic methylmercapto-6-dimethylaminopurine to form properties of the acetamido group.' By use of the the desired nucleoside. Although this method was N-phthalyl blocking group, the resultant nonsatisfactory for synthesis of nucleosides from basic phthalimido group should allow preparation 2-methylmercapto-6-dimethylaminopurine, some- of a chlorosugar such as V by use of the elegant times in other cases undesirable anomerization, ether-hydrogen chloride method, thus, completely isomerization or decomposition products were also avoiding the use of titanium tetrachloride. Another objection to the N-acetyl blocking formed. For example, this method with chloromercuri-6-benzamidopurine gave the expected 9-p- group is that i t can be base hydrolyzed to the nucleoside, but also produced the corresponding a- amine only when the acetamido group is adjacent ~ ~ difficulty is again surto a c i s - h y d r ~ x y l . ~This nucleoside.? Reaction of l-O-acetyl-2,5-di-O-benzomounted by the N-phthalyl blocking group which y~-3-acetamino-3-deoxy-~-arabinofuranose with titanium tetrachloride followed by condensation with can be removed selectively by hydrazine' t o form 2 - methylmercapto - 6 - dimethylaminopurine gave, am inonucleosides. I n order to establish the usefulness of the Nafter desulfurization and debenzoylation, not only phthalyl blocking group for synthesis of aminothe expected B-dimethylamin0-9-(3'-acetamino-3'deoxy-a-D-arabinofuranosyl)-purine,but some of nucleosides, four distinct problems could be envisioned. These were investigated in order of dethe corresponding a-D-ribofuranosyl-purine. (4) J. Davoll, B. Lythgoe and A. R. Todd, J . Chcm. Soc., 967 ( 1 ) B. R. Baker, R . E. Schaub, J. P. Joseph and J. H. Williams, THISJ O U R N A L . 77, 12 (19%), Paper I X of this series. (2) B. K. Baker, R . R . Schaub a n d H. If.Kissman, i b i d , 77, 5911 (IO.?iR), paper XV rrf this series. (3) B . R. Baker a n d R . R . S r h a u h , i b i ( i . ,77, 23RG ( l ! l , i 2 ) , Paper S I 1 of this series.
( 1 948). (5) B . R . Baker, J . P. Joseph, R. E. Schaub and J. H. Williams, J . Org. Chem., 19, 1786 (1954), paper V of this series, ( 6 ) B. R. Baker, J. P. Joseph and J. H . Williams, THISJ O U R N A L . 77, 1 (19.55). paper VI1 of this series. ( 7 ) 11. In:: n n d R . hlnnske. J . C h e m Suc., 2 3 i 8 (l9!X),
5906
B. R. BAKER,J. P. JOSEPH
AND
R.E. SCHAUB
Vol. 77
creasing availability of compounds for study rather than on the basis of continuity as follows. The first aroblem was to establish whether or not the blocking groups from an N-phthalyl-2’,5’-di-OHOCH, acyl aminonucleoside I1 could be removed without NaOMe disruption of the nucleoside, since I1 would be the c--type of a blocked nucleoside obtained as an interN OCOR / \ , \ o=c c=o mediate during coupling of a blocked halo sugar 0.c c=o \ / \, ChHl with a purine. Treatment of 6-dimethylamino-9kn4 m I (3‘-amino-3’-deoxy-~-~-ribofuranosyl)-purine (VI),6 “the aminonucleoside,” with phthalic anhydride in boiling dimethylformamide gave a 92% vield of crystalline N-phthalyl aminonucleoside 111. The latter on benzoylation with benzoyl chloride in pyridine a t 100’ gave the dibenzoate IIb, isolated as a crystalline hemi-hydrate in 95y0 yield. Similarlv acetylation of I11 with acetic anhydride in pyridine a t 100’ gave the crystalline diacetate I I a P in 95% yield. The preparation of I I a could be further simplified by reaction of the aminonucleoside VI with phthalic anhydride in pyridine to give a solution of a phthalamic acid which, by addition of acetic anhydride, was ring closed to the phthalimido derivative and 0-acetylated simultaneously to form IIa in 97YGover-all yield from VI. Debenzoylation of the hydrate of the N-phthalyl di-0-benzoyl aminonucleoside I I b with 1 mole of methanolic sodium methoxide proceeded with concurrent ring opening of the phthalimido group to a sodium phthalamate derivative.8 When the crude sodium phthalamate was refluxed in dimeth- the action of hydrazine7 in methyl Cellosolve folylformamide containing 2 moles of acetic acid, lowed by elimination of the phthalyl group as ring closure back to the N-phthalyl aminonucleo- phthalhydrazide by treatment with acetic acid.6 The second problem was cleavage of the blocked side I11 took place in 51y0 over-all yield from IIb. I1 to a blocked aminosugar (I or aminonucleoside This difficulty of ring opening of the phthalimido IV) suitable for synthesis of other nucleosides. Atgroup was partially avoided by removal of water of 6-dimethylamino-9-(2‘,5’tempted hydrolysis of crystallization by treatment with acetic anhydride di-O-benzoyl-3‘-phthaIimido-3 ‘-deoxy - 0- D - ribofurprior to debenzoylation of IIb, the N-phthalyl aminonucleoside 111 being obtained directly in 6570 anosy1)-purine (IIb) with the boiling two-phase sysyield. By cyclization of the sodium phthalamate tem 2 N hydrochloric acid-ethylene dichloride, conditions successfully used with the corresponding in the mother liquor an additional 27% of I11 was 3’-acetamido nucleoside,’ failed since most of the obtained. Drying of I I b by distillation with toluI I b was recovered unchanged and no reducing sugar ene gave 48YGof 111 directly and an additional 3870 was formed. This difficulty was surmounted by was obtained by refluxing in dimethylformamide. cleavage of the nucleoside with 30% hydrogen broSimilarly, the N-phthalyl di-0-acetyl aminonu- mide in acetic acid, followed by hydrolysis of the recleoside I I a was catalytically deacetylated under as sultant bromo sugar with water and silver carbostrictly anhydrous conditions as possible in metha- nate,g 2,5-di-0-benzoyl-3-phthalimido-~-ribofurannol-chloroform containing 30 mole yo of sodium ose (Ib) being formed in 83y0yield as a strongly remethoxide to 65% of 111. From the mother liquor ducing glass. Acetylation in pyridine gave a mixcould be isolated 13y0of the corresponding crystal- ture of anomeric 1-0-acetates IVb, from which one line phthalamic acid. If no effort was made to keep anomer, presumably the CY,was crystallized in 57% the reaction strictly anhydrous, 1mole of water was yield. Similarly, hydrogen bromide cleavage of gradually absorbed over 1.5 hours in boiling metha- I I a followed by treatment with silver carbonate and nol since a total of slightly more than 1 mole of so- acetylation gave a 63y0over-all yield of the crystaldium methoxide was necessary to keep the reaction line anomer of 1,2,5-tri-O-acety1-3-phthalimido-3mixture basic. The intermediate phthalamate de- deoxy-D-ribofuranose (IVa). rivative was then recyclized by treatment with Direct acid-catalyzed acetolysis of the N-phthalyl ethyl chlorocarbonate and triethylamine in di- di-0-acetyl aminonucleoside I I a to the crystalline methylformamides giving 111 in 55% yield. triacetate IVa, proceeded in an optimum yield of The aminonucleoside VI could be regenerated 82%,’O the ratios of sulfuric acid, acetic acid and from its N-phthalyl derivative I11 in 85% yield by (9) R. K. Ness, H. W. Diehl and H. G. Fletcher, THIS JOURNAL, 7 6 ,
R!
i
( 8 ) I t has been well k n o m n f o r many years that the phthalimido group is rapidly opened to a sodiiim phthalamate with sodium hydroxide; cf. R . Andreasch, Mnnatsh.. 25, 774 (1904); J. v. Braun, Bo.,37, 3586 (1904); S.Gabriel and J. Wiener, ibid., 21, 2670 (1888); S. Ga11rit-I and 1‘ Posner iJii,l , 2 7 , 10.13 (1894); I.. Reese, A n n . , 242, 1 (1887).
2624 (1953); 76, 763 (19541,have used this sequence of reagents for conversion of methyl 2,3,5-tri-O-benzoyIpentofuranosides t o 2,3,5tri-0-benzoylpentoses. (10) About 1% yield of 1,1,2,4,5-pento-O-acetyl-3-phthalimldo-3deoxy-D-ribose m p. 16Q0,was obtained as a by-product in this acetolysis reactiiin.
Nov. 20, 1955
SYNTHESIS OF AMMONUCLEOSIDES
5907
acetic anhydride" were varied. Similarly, acetoly- part to the insolubility of the compounds in the sis of the di-0-benzoyl nucleoside, IIb, to the crys- solvent system-and was not considered practical. talline anomer of l-O-acetyl-2,5-di-O-benzoyl-3- Since chloromercuri-6-dimethylaminopurinegave phthalimido-3-deoxy-~-ribofuranose(IVb) pro- a mixture of the 7- and 9-nucleoside, IIb and VIIb, ceeded in 7770 yield. Equilibration'' of the ano- the condensation of 2,5-di-O-benzoyl-3-phthalimeric 1-0-acetate in the mother liquor gave an mido-3-deoxy-~-~-ribofuranosyl chloride (Vb) with additional 9% of IVb. chloromercuri-2-methylmercapto-6-dimethy1am~n0The third problem was resynthesis of nucleosides purine was investigated since in previous work the from the blocked 3-phthalimido-~-ribofuranoses,latter had orientated an incoming sugar only to the IV. As expected the phthalimido group did not 9 - p o ~ i t i o n . ~ , ~ The . ~ ~ crude , ~ ~ 2-methylmercaptoform an insoluble hydrochloride with ethereal hy- 6-dimethylamino-9-(2',5'- di-0- benzoyl - 3'- phthalidrogen chloride, the 0-triacetate IVa being con- mido-3'-deoxy-P-~-ribofuranosyl)-purine (VIII) verted to a crude chloro sugar Va in 71-75% yield. could not be obtained crystalline. Desulfurization This chloroaceto sugar condensed poorly with with Raney nickel did not give the expected IIb. The A test run with Raney nickel showed that the IIb chloromercuri - 6 - dimethylaminopurine. blocked nucleoside I I a could not be crystallized, was attacked by the reagent in some deep-seated but 0-deacylation gave 5-10y0 over-all yields of manner since I I b could not be recovered even when 111. Since 2,3,5-tri - 0 -benzoyl - D - ribofuranosyl the product was worked up with the assumption chloride has been shown to give better yields of a that either partial debenzoylation or ring opening nucleoside than 2,3,5-tri-0-acetyl-~-ribofuranosyl to a phthalmic acid had taken place. chloride, l 2 the use of l-O-acetyl-2,5-di-O-benzoyl-3- Debenzoylation and dephthalation of the crude phthalimido-3-deoxy-~-ribofuranose (IVb) was in- blocked methylmercapto nucleoside gave 1370 vestigated. Reaction of IVb with ethereal hydro- over-all yield of crystalline 2-methylmercapto-Ggen chloride proceeded smoothly to the stable, dimethylamino - 9 - (3'-amino-3'-deoxy-P-~-ribofuracrystalline ribofuranosyl chloride, Vb, m.p. 160- nosy1)-purine (IX) when the product was isolated 162', in 98% yield, which had the P-c~nfiguration.'~ by absorption on a carboxylic acid type resin.2 Condensation of the crystalline Vb with chloro- Desulfurization afforded the aminonucleoside VI mercuri-B-dimetE.ylarninop~rine~~ in boiling xylene from puromycin in 32y0 yield, thus proving the pproceeded smoothly forminq the crystalline blocked configuration of IX.15 9-P-nucleoside I I b in 47% yield, m.p. 128-130'. T t is clear that for synthesis of aminonucleosides The latter gave no depression in m.p. when mixed with a 6-dimethylaminopurine moiety the earlier with IIb (m.p. 130-132') prepared from III.15 method using the N-acetyl blocking group with tiHowever, the ultraviolet spectrum showed con- tanium tetrachloride' is preferred. However, for tamination of the resynthesized I I b with the 7- synthesis of aminonucleosides from adenine2 the nucleoside VIIb since along with the major peak a t N-phthalyl blocking group method is preferred. 275 mp there was a large inflection a t 295 rnp.l6 Thus it appears that the two methods can be comFrom the relative molecular extinctions a t 275 and plementary. 295 mp,14i t was estimated that the 9-nucleoside I I b The fourth and final problem for completion of was contaminated with 18-26% of the 7-nucleoside the use of the N-phthalyl blocking group was to VIIb. These two nucleosides did not separate on prepare l-0-acetyl-2,5-di-0-benzoyl-3-phthalimidorecrystallization, but the pure 9-isomer could be iso- 3-deoxy-~-ribofuranose(XIII) by total synthesis. lated by partition chromatography on CeliteL2using Catalytic deacetylation of methyl 2,s-di-0-acetyl3-acetamido-3-deoxy-p-~-ribofuranoside (Xb), prethe system water-methanol-ethyl acetate-petroleum ether (90-100') in the ratio of 1:25:5:25. viously synthesized from D-Xylose,l7 gave crude The 9-nucleoside I I b was eluted first and no at- X I b which was hydrolyzed with hot barium hydroxtempt was made t o isolate the 7-nucleoside VIIb. ide to methyl 3-amino-3-deoxy-/3-~-ribofuranoside However, the process gave poor recoveries-due in (XIIb). The latter was not purified, but reacted directly with phthalic anhydride in dimethylforma-
(11) The use of these reagents for acetolysis of methyl glycoside a Series, o( -Configuration acetates to fully acetylated glycosides has been described: cf. N. K. 63, 1727 (1941); 65, Richtmyer and C. S. Hudson, THISJOURNAL, b Series ,8 Confiquration 740 (1943): B. R. Baker and R. E. Schaub, J . Org. Chcm., 19, 646 AcOCH, HOCHZ (1954), paper I11 of this series. (12) H. M. Kissman, C. Pidacks and B. R. Baker, THISJOURNAL, QOMe ~ H o c ~ O M Ea (OH)2, e 77, 18 (1955), paper X I of this series. (13) When this chloro sugar Vb in dioxane was allowed to react with NHz OH NHAc NHAc 2 moles of water the initial specific rotation gradually changed from X XI +75O t o 4-121' over a period of 24 hours, thus showing the 8-configuration of Vb; cf. H. G. Fletcher, Jr., and R. K. Ness, THISJOURNAL, 76, 760 (1954). In 18:7 dioxane-water the hydrolysis was complete in less time than that required to measure the initial rotation ErOCH, (three minutes), a specified rotation of +116' being observed which did not change further in 3 hours. (14) B. R . Baker, J. P . Joseph and J. H. Williams, J . Org. Chcm., 19, 1780 (1954), paper I V of this series. (15) This formation of a 1,2-trans-nucleoside IIb from a l,2-transhalosugar Vb verifies the previous prediction, that double Walden inversion should occur during nucleoside formation from a 1 ,Z-transXIP halosugar. (161 7-Glycosides of 6-dimethylaminopurine have Xmax 297 mfi (17) B. R . Baker, R . E. Schaub and J. H. Willi%ms,T H I SJOURNAL, whereas the corresponding 9-nucleosides have Xmar 275 mp.l( 77, 7 (19551, paper VI11 of this series. ~
-
w m
,5908
R.R.RAKER,J. P. JOSEPFI A N D R.E. Scrrarrn
VOl. '77
mide to give the crystalline N-phthalyl derivative readily dissolved in 2 cc. of water. The solution was clariXVb in 49% over-all yield from Xb. Benzoylation fied by filtration and acidified with acetic acid. After standing overnight the white crystals of the phthalamic acid, gave the non-crystalline dibenzoate XIVb which 6-dimethylamino-9-(3 ' - (o - carboxybenzamido) - 3 '-deoxy-6was subjected to acetolysis with acetic anhydride- D-ribofuranosy1)-purine were collected; yield 57 mg. (13%). acetic acid-sulfuric acid forming crystalline 1-0-m.p. 180-182' (gas), resolidifies and remelts at 277-278" dec. acetyl-3,5-di-O-benzoyl-3 - phthalimido - 3 - deoxy - D- (the m.p. of 111). same phthalamic acid was obtained by solution of ribofuranose (XIII), identical with the same com- 300This mg. of I11 in 2 cc. of warm 1 N sodium hydroxide folpound IVb obtained by degradation of puromycin lowed by acidification t o p H 4 with acetic acid and standing and in 6170 over-all yield from XV. Similarly overnight to complete crystallization; yield 238 mg., m.p. XI11 could be obtained from methyl 2,5-di-0-ace- 182-184 (gas) followed by resolidification. Recrystallizafrom methanol gave a methanol solvate, m.p. 175-178" ty~-3-acetamido-3-deoxy-a-~-ribofuranos~de (Xa) in tion (gas) followed by resolidification. about the same over-all yield as in the p-series. Anal. Calcd. for C~~H~~IYGOGCHIOH: C, 53.2; H , Acknowledgment.-The authors are grateful to ,552; N, 17.7. Found: C, 53.6; H, 5.59; N, 17.9. L. Brancone and staff for the microanalyses, to W. This compound showed absorption in the infrared at 2.93, Fulmor and staff for the rotations and spectro- 3.03, 3.13 I.L (OH, NH), 5.77 u (COOH), 5.98, 6.42 p photometric data and to C. Pidacks for the partition (:imide) and 6.20 /1 (C=N). Regeneration of 6-Dimethylamino-9-(3'-amino-3'-deoxychromatogr9,phy. 6-D-ribofuranosy1)-purine(VI) from 111.-A solution of 1.00 O
Experimental 6-Dimethylamino-9-(3 '-phthalimido-3 '-deoxy-P-D-ribofuranosy1)-purine (111). (A).-A mixture of 5.0 g. of the arninonucleoside VI,6 2.8 g. of phthalic anhydride and 25 CC. of dimethylformarnide was refluxed for 45 minutes, solution being complete a t the b.p. The cooled solution was poured into 250 cc. of water with stirring, the product was collected on a filter and washed with water; yield 6.6 g. (92%), m.p. 274-278' dec. Recrystallization of a similar preparation from alcohol gave white crystals, m.p. 276277" dec., [ C U ] * ~ D-186' (2% in pyr.); 3.00, 3.07 p (OH); 5.63, 5.82 u (phthalyl C=O); 6.23 p (C=N). Amd. Calcd. for CioHzoNeOj: C, 56.6; H , 4.72; S , 19.8. Found: C, 56.8; H, 4.54; K,19.4. (B).-A solution of 350 mg. of I I b hydrate and 0.66 cc. of 1 ,li methanolic sodium methoxide in 10 cc. of methanol was refluxed for 30 minutes, then evaporated to dryness in Z ~ C U O . The residual sodium phthalamate derivative was refluxed in 3 cc. of dimethylformamide containing 0.66 cc. of glacial acetic acid for 30 minutes. The cooled solution was poured into a stirred mixture of 10 cc. of benzene and 30 cc. of water to remove methyl benzoate. The product was collected by filtration and washed with water and benzene; yield 120 mg. (51%),m.p. and mixed m.p. with prepnration A 274-276' dec. (C).-A solution of 1.00 g. of I I b hydrate in 5 cc. of acetic anhydride was heated on the steam-bath for 1 hour, then evaporated to dryness in vaczLo. The residue was thrice evaporated with 5-cc. portions of xylene to remove traces of acetic anhydride leaving anhydrous I I b as a glass. The residue was dissolved in 2.5 cc. of reagent chloroform and 7.5 cc. of reagent methanol. It was necessary to add 0.73 cc. (40 mole %) of 1 X methanolic sodium methoxide over a period of several hours t o keep the pH > 10 when spotted on moist indicator paper. After 18 hours more in a stoppered flask, the product was collected on a filter and washed with methanol; yield 430 mg. (63p'j, m.p. and mixed m.p. with preparation A, 277-278' dec. The filtrate was evaporated to dryness in znczio. The residue was dissolved in 3 cc. of dimethylformarnide coutaining 0.04 cc. of acetic acid and refluxed for 30 minutes. The cooled solution was poured into 30 cc. of water and 10 cc. of benzene giving an additional 173 mg. (279'') of product, m.p. and mixed m.p. with preparation A, 273-278" dec. If the I I b mas dehydrated by refluxing a toluene solution under a constant water separator until anhydrous, the solvent removed and the debenzoylation carried out as above 40 mole yo of sodium methoside wv;ts required. From the debenzoylation solution, 48Y0 of product was obtained. Refluxing the residue from the mother liquor in dimethylformamide as above gave an additional 38y0of 111. (D).-To a solution of 508 mg. of IIa (dried 8 hours a t 11 in high vacuum over P20s) in 1.5 cc. of methylene chloride was added 3.5 cc. of reagent methanol and 0.30 cc. of 1 N methanolic sodium methoxide. The solution was allowed to stand in a stoppered flask for 3 hours. The product was collected on a filter and washed with methylene chloride; yield 280 mg. (64y0), n1.p. 267-269" dec. The to dryllrss zn w c m . The residue filtr:rt
