Tetrahedron Letten No. 9, pp 657 - 660, 1973. Perguan Preoo. Printed In Great Itrltain,

KP. wdhi, war mgh, T.D. Bturu rad abL kkh0rji Deputmnt of Chmlatry, lDmLl*~~unlvv~ltY,

v .

(Received in lJJC 29 December 1972; accepted for publication 17 January 1973)

W!ltkop (1) ha8 recently reported that dlhydmthymldlne (I)

undergoor Uualalen-blber type photohydmly8is to the urea

derivative (II) and that the change I +I1 imolver an intrualeculu

hydrogen trUD8fer through a sItmembered truuition rtate (A).

I

FFH, deoxyribose

Further to O\lr work On the photOlp8i8 Of rteroidil la&us pO88088iw

Un8atUratiOn In the vicinity of the lactam molaty (21, we have 8tudled

the photochemIcal behariour of 3~~oetoq-l6,l'l-reoo-~-~rortur-

16,17-lmlde (III) and report herein an interesting Ob8Omation (3).

657

65s No. 9

Irr8dlation 0r 0.7 g 0r III (4) in TEP r0r a total 0r 48 hrs gave,

after ohromatography (silio8 gel; bensene-ethyl l oetate, 23~21,

0.15 g Or Iv, ap L83-94’, besides the unaffeoted (III) aud an

latraotahle oil (5). The struoture of IV is brought out oompletely

r- its various rpeotra. Its mass speotrum (m/e 33&M+, 24% oi the

bare peak at a/e 197) eahlblted loss of 28 mass writs (CO) in the

transr0=tion III *IV. Its solid phase IR speotrum (nuJo1) revealed

it to be a primary tide (\) Ilax 164c) CB-~, amide band II; 16% OH-‘, amide band I; 3395 and 3210 orm1, R-H) (6) confirmed by the observation

or a broad two-proton signal in its m between s 6.00-5.80 (q) (7);

in III, the imldlo H appeared as a broad sfnglet around S 8.48.

Rtrther, the WIR spectrum of IV showed only one t-methyl singlet

at SO.94 suggesting obviously particlpatloa 0r Cl30methyl (in III,

b 1.23) during its couverslon Into IV(a). The fate of this methyl

becue known with the observation of two little singlets (in IV)

located respectively at s 4.80 (4 4 HE) and s4.67 (4 4 Hs)

iadlcative of two terminal oleflnlo hydrogen8 having a small g&nil

ooupllng between them (or. 9).

Presumably, the phototransformation III 3 IV involves

interception by a seven-membered ayclic transition state la an

intramolecular hydrogen transfer (C+D, aeohanlstlc scheme) though

the loss of CO in the solution phase photolysis of the amide is

unexaeptlonal (10).

Our preference for the Initial CO-W bond cleavage In III (leading to dlradlcal B) is based purely on our experience with other amides (2) although there is nothing to exclude role of the dlradical resulting rr0n initial ~s-co bond fission.

lo. 9 659

AC AC0

B

References and Faotnotes

C

1.

2.

Y. Xondo and B. wltkop, J. Am. them. Qbc., 8, 3258 (1968).

R. p. Gandhi, Majar slngh, P. P. Sachdeva and 5. Me MdhOrjl,

St. l&t., Preoedlng comunlcatioa.

No. 9 660

3.

4.

5.

6.

7.

8.

9.

10.

Abstracted in part from Ph.D. dissertation of Majar Slngh,

bwkshetra IMverrity, India, 197l.

Made aooordfng to REI, Regan and F.H. Rayer, J. Am. Chew QOc.,

z, 639 (lBS6). The rtructure of III was checked through its

RHR and ma88 rpectra.

?botolyris war carried out with a 250 watts medium pressure

mercury lamp in a quartz vessel using nitrogen atmosphere.

C.R.R. Rao, ~Cheeical Applications & IR speotroscopy’,

Acadsaslc Press, Iondon, 1963, pa 258.

The 6-oleflnic Ii multlplet in IV showed up at sS.50 - 5.32.

RHR and mass spectra were recorded respectively on a Varlan

A-60-D machine (on CDC13 solutions) and a CRC model 2101lOB

rpectrometer.

f.6, E?bacea and D.H. Willlams, ‘Applications of RMR

spectroscopy to Organic Chemistry’, Holden-Day, 1964, p. 57.

C.H. Richollr and PA. Leermakerr, J. Org. Chem., 35, 2764 (1970).