Phytochemistry, Vol 27, No 5, pp 1479 1482, 1988 0031 9422/88 $300+000 Printedm GreatBritain Pergamon Press plc LIGNANS OF PIPER TRICHOSTACHYON S K KOUL, S. C. TANEJA, P PUSHPANGADAN and K L. DHAR* Natural Products Chemistry Dwlsmn, Regional Research Laboratory, Jammu Taw~ 180001, India (Rewsed recewed2 October 1987) Key Word lndex--Pzper tmchostachyon; Plperaceae; dehydrotnchostm; ( - ) hmokmin, (-)-cubebm, tnchostm, ( -)-dihydrocubebin, &hydromchostm, 13 C NM R, CD Abstract--From the petrol extract of Ptper trtchostachyon, six llgnans have been isolated Three of them were identified as the known compounds (-)-hmokmin, (-)-cubebin and (-)-&hydrocubebm The other three were new compounds and were assigned the structures 2S,3S,3-(6-methoxy 1,3-benzodloxol 5-yl) methyl 4-(1,3-benzodioxol 5- yl)methyl tetrahydrofuran-2-one, 2S,3S,3-(6-methoxy 1,3-benzodloxol 5-yl)methyl 4-(1,3-benzodioxol 5-yl)methyl tetrahydrofuran-2-ol and 2S,3S,2-(6-methoxy 1,3-benzodmxol 5-yl)methyl 3-(1,3-benzodloxol 5-yl)methyl butan 1,4- diol INTRODUCTION Previous work on the stems [1-4] and the leaves [5, 6] of Ptper trichostachyon DC have shown the presence of aromatic and acychc and cychc long chain amides, e.g. trichostachine and cyclostachme, besides other common ahphatlc compounds [7]. Our chemical investigations on the fruits of this plant have shown it to be devoid of such amides. Instead, we have isolated and Identified six hg- nans (1-6), three of which [dehydrotnchostm (2), trlchos- tin (4) and dlhydrotnchostm (6)] are new to the litera- ture. RESULTS ANDDISCUSSION Llgnan 2 had the molecular formula C21HzoO 7 (M + m/z 384) and its IR spectrum showed a characteristic band for a 7-1actone carbonyl at 1775 cm- 1. Its 1H NMR spectrum displayed signals characteristic of a dlaryl bu- tyrolactone. Signals for methylenedloxy protons were observed as a smglet at 6 5.90 and for an aromatic meth- oxyl at 63 90 Aromatic protons were observed as a H R~ 1 R H._O/0~ R2 ~~,~LCH2 0H o R j R 2 I =O H 5 H 2 ~--0 OMe 6 OMe 3 OH H 4 OH OMe *Author to whom correspondence should be addressed slnglet at 66 26 (2H) for H-2 and H-6 and a multlplet at ,56 29 to 6 73(3H) for H-2', H-5' and H-6' A multiplet centred at 64.0 was assigned to the methyleneoxy pro- tons of the lactone Two methlne protons (/~,ff) of the butyrolactone system were observed alongwlth the pro- tons of one of the benzylic groups centred at 62 50 as a multlplet A signal for the other benzylic protons was observed as a narrow envelope centred at 62.80. The 1H NMR data of hlnokmln and compound 2 were very similar except for the appearance in 2 of an extra signal attributed to one methoxyl at 63 90. This was supported by mass spectrum, which differed from that of hmoklnin by 30 The trans stereochemtstry of the two benzyl groups was estabhshed by 1H NMR, 13C NMR, CD and optical rotation when compared with hmokmm [8-11] Both showed negatwe Cotton effect m CD (287, 240 and 285, 243 nm respectwely) and both were optically laevoro- tatory In the 13CNMR spectrum of 2 the 3,ff carbons were located at 646.5 and 41.4 which was m accordance with the values of these carbons in hmokmin [12]. The mass spectrum proved helpful m establishing the posmon of the aryl moiety carrying a methoxyl group towards the carbonyl in the lactone ring The formation of the ion at m/z 222 and its further fragmentatmn to'the ion at m/z 192 confirmed unambiguously the position of the two hgands m trichostm (Fig. 2) The diognostic fragments for the other part of the molecule appeared at m/z 162 and 132. The second new substance (4) had a molecular formula C 2IH2207 (M + m/z 386) and its IR spectrum contained a broad band at 3400-3420 cm- 1 for a hydroxyl function In ~ts 1H NMR spectrum, signals for methoxyl and meth- ylene&oxy protons were observed at 63.86 and 5 80 respectively and for five aromaUc protons at 66 0-6 68 as a multiplet A broad singlet at 65.10 showed the presence of a hemi-acetahc proton which on acetylation was shif- ted downfield and merged with the signal of the meth- ylenedioxy protons, while the other signals remained practxcally unchanged. This was also supported by the 13 C NMR data where the hemi-acetalic carbon was ob- served at 6103 3 as a doublet The compound showed 1479